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  <xsd:element abstract="true" id="ato_AccumulatedNetGainLossFromCommodityContractsCashFlowHedgesMemberMember" name="AccumulatedNetGainLossFromCommodityContractsCashFlowHedgesMemberMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_AccumulatedNetGainLossFromInterestRateHedgesMemberMember" name="AccumulatedNetGainLossFromInterestRateHedgesMemberMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_AccumulatedOtherComprehensiveIncomeDisclosureTextBlock" name="AccumulatedOtherComprehensiveIncomeDisclosureTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_AccumulatedOtherComprehensiveIncomeLossAbstract" name="AccumulatedOtherComprehensiveIncomeLossAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnitsDiscontinuedOperations" name="AmountOfDilutiveSecuritiesStockOptionsAndRestrictiveStockUnitsDiscontinuedOperations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_AnticipatedDebtIssuanceAmount" name="AnticipatedDebtIssuanceAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_AptAnnualAdjustmentMechanismMember" name="AptAnnualAdjustmentMechanismMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_AuthorizedCommercialPaper" name="AuthorizedCommercialPaper" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments" name="AvailableForSaleSecuritiesGrossUnrealizedGainAccumulatedInInvestments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="ato_AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments" name="AvailableForSaleSecuritiesGrossUnrealizedLossAccumulatedInInvestments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_AvailableForSaleSecuritiesSupplementalExecutiveBenefitPlans" name="AvailableForSaleSecuritiesSupplementalExecutiveBenefitPlans" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_BusinessLicenseTaxAbstract" name="BusinessLicenseTaxAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_BusinessLicenseTaxExaminationDescription" name="BusinessLicenseTaxExaminationDescription" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_BusinessLicenseTaxExaminationSettlementAmount" name="BusinessLicenseTaxExaminationSettlementAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_CashFlowHedgeGainLossImpactonEarnings" name="CashFlowHedgeGainLossImpactonEarnings" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_CashFlowHedgeGainLossIncludedInCostOfSalesNet" name="CashFlowHedgeGainLossIncludedInCostOfSalesNet" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_CashFlowHedgeGainLossReclassifiedtoPurchasedGasCostNet" name="CashFlowHedgeGainLossReclassifiedtoPurchasedGasCostNet" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_CashFlowHedgeLineItems" name="CashFlowHedgeLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_CashFlowHedgeTable" name="CashFlowHedgeTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_CommitmentsandContingenciesAbstract" name="CommitmentsandContingenciesAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_CommittedFacilityNonregulatedOperationsMember" name="CommittedFacilityNonregulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_CommodityContractGainLossReclassifiedToEarnings" name="CommodityContractGainLossReclassifiedToEarnings" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_CommodityContractOutstandingVolumesLineItems" name="CommodityContractOutstandingVolumesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_CommodityContractOutstandingVolumesTable" name="CommodityContractOutstandingVolumesTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_CommonStockParValuePerShare" name="CommonStockParValuePerShare" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_CurrentYearBenefitPlanContributionsAbstract" name="CurrentYearBenefitPlanContributionsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_DebtAndEquitySecuritiesAuthorizedForIssuance" name="DebtAndEquitySecuritiesAuthorizedForIssuance" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_DebtAndEquitySecuritiesAvailableForIssuance" name="DebtAndEquitySecuritiesAvailableForIssuance" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_DebtInstrumentCovenantExcessDebtTrigger" name="DebtInstrumentCovenantExcessDebtTrigger" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_DeferredChargesAndOtherAssetsMember" name="DeferredChargesAndOtherAssetsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_DeferredCreditsAndOtherLiabilitiesMember" name="DeferredCreditsAndOtherLiabilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_DeferredFranchiseFeesLiabilityMember" name="DeferredFranchiseFeesLiabilityMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element abstract="true" id="ato_DeferredGasCostsLiabilityMember" name="DeferredGasCostsLiabilityMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_DeferredMiscellaneousCostsMember" name="DeferredMiscellaneousCostsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element id="ato_DerivativeAssetContractNetting" name="DerivativeAssetContractNetting" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element id="ato_DerivativeCashCollateral" name="DerivativeCashCollateral" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="ato_DerivativeLiabilityContractNetting" name="DerivativeLiabilityContractNetting" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="ato_DerivativeLiabilityNetofContractNetting" name="DerivativeLiabilityNetofContractNetting" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_DescriptionOfPendingLitigation" name="DescriptionOfPendingLitigation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_DiscontinuedOperationCashPriceReceivedFromDisposalOfDiscontinuedOperation" name="DiscontinuedOperationCashPriceReceivedFromDisposalOfDiscontinuedOperation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="ato_DiscontinuedOperationsMiscellaneousIncomeExpense" name="DiscontinuedOperationsMiscellaneousIncomeExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_DiscontinuedOperationsPurchasedGasCost" name="DiscontinuedOperationsPurchasedGasCost" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
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  <xsd:element abstract="true" id="ato_EarningsPerShareDilutedDiscontinuedOperationsAbstract" name="EarningsPerShareDilutedDiscontinuedOperationsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_EffectonNetPeriodicCostDueToDiscountRateChangeRemainingFiscalYear" name="EffectonNetPeriodicCostDueToDiscountRateChangeRemainingFiscalYear" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
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  <xsd:element abstract="true" id="ato_ExpectedRecognitionInEarningsOfDeferredGainLossesFinancialInstrumentsAxis" name="ExpectedRecognitionInEarningsOfDeferredGainLossesFinancialInstrumentsAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_ExpectedRecognitionInEarningsOfDeferredGainLossesFinancialInstrumentsDomain" name="ExpectedRecognitionInEarningsOfDeferredGainLossesFinancialInstrumentsDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_ExpectedRecognitionInEarningsOfDeferredGainLossesFinancialInstrumentsTable" name="ExpectedRecognitionInEarningsOfDeferredGainLossesFinancialInstrumentsTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
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  <xsd:element id="ato_FairValueHedgeTimingIneffectiveness" name="FairValueHedgeTimingIneffectiveness" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="ato_FairValueMeasurementsPolicyTextBlock" name="FairValueMeasurementsPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_FirstFacilityRegulatedOperationsMember" name="FirstFacilityRegulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_GainLossOnDerivativeInstrumentsNotDesignatedHedgesNetPretax" name="GainLossOnDerivativeInstrumentsNotDesignatedHedgesNetPretax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_GainLossOnHedgeIneffectiveness" name="GainLossOnHedgeIneffectiveness" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_HedgePercentageOfActualHeatingSeasonGas" name="HedgePercentageOfActualHeatingSeasonGas" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_HedgeVolumeOfActualHeatingSeasonGas" name="HedgeVolumeOfActualHeatingSeasonGas" nillable="true" substitutionGroup="xbrli:item" type="num:volumeItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_HedgedPortionOfGasStoredUndergroundFairValueDisclosure" name="HedgedPortionOfGasStoredUndergroundFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_IntercompanyFacilityNonregulatedOperationsMember" name="IntercompanyFacilityNonregulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_IntercompanyFacilityRegulatedOperationsMember" name="IntercompanyFacilityRegulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_IntercompanyPayables" name="IntercompanyPayables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_IntercompanyReceivables" name="IntercompanyReceivables" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="ato_InterestRateAgreementGainLossReclassifiedToEarnings" name="InterestRateAgreementGainLossReclassifiedToEarnings" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_InterestRateHedgesSeniorNotes2015IssuanceMember" name="InterestRateHedgesSeniorNotes2015IssuanceMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element abstract="true" id="ato_InventoriesUnderIndexedContractsMember" name="InventoriesUnderIndexedContractsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element id="ato_LongTermPurchaseCommitmentMinimumQuantityRequiredAfterThreeYears" name="LongTermPurchaseCommitmentMinimumQuantityRequiredAfterThreeYears" nillable="true" substitutionGroup="xbrli:item" type="num:volumeItemType" xbrli:periodType="instant" />
  <xsd:element id="ato_LongTermPurchaseCommitmentMinimumQuantityRequiredOneToThreeYears" name="LongTermPurchaseCommitmentMinimumQuantityRequiredOneToThreeYears" nillable="true" substitutionGroup="xbrli:item" type="num:volumeItemType" xbrli:periodType="instant" />
  <xsd:element id="ato_LongTermPurchaseCommitmentMinimumQuantityRequiredWithinOneYear" name="LongTermPurchaseCommitmentMinimumQuantityRequiredWithinOneYear" nillable="true" substitutionGroup="xbrli:item" type="num:volumeItemType" xbrli:periodType="instant" />
  <xsd:element id="ato_LossContingencyCompensatoryDamagesAwardedValue" name="LossContingencyCompensatoryDamagesAwardedValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="ato_MaximumHedgePercentageOfAnticipatedHeatingSeasonGas" name="MaximumHedgePercentageOfAnticipatedHeatingSeasonGas" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_MediumTermNotesDue2025Member" name="MediumTermNotesDue2025Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_MergerAndIntegrationCostsNetMember" name="MergerAndIntegrationCostsNetMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_MidTexDivisionMember" name="MidTexDivisionMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_MinimumHedgePercentageOfAnticipatedHeatingSeasonGas" name="MinimumHedgePercentageOfAnticipatedHeatingSeasonGas" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_MinimumLengthOfTimeHedgedInCashFlowHedge" name="MinimumLengthOfTimeHedgedInCashFlowHedge" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_MiscellaneousRegulatoryLiabilitiesMember" name="MiscellaneousRegulatoryLiabilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_NaturalGasDistributionSegmentMember" name="NaturalGasDistributionSegmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_NetIncomeLossFromDiscontinuedOperationsAvailableToCommonStockholdersBasic" name="NetIncomeLossFromDiscontinuedOperationsAvailableToCommonStockholdersBasic" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_NetIncomeLossFromDiscontinuedOperationsAvailableToCommonStockholdersDiluted" name="NetIncomeLossFromDiscontinuedOperationsAvailableToCommonStockholdersDiluted" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_NextTwelveMonthsMember" name="NextTwelveMonthsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element id="ato_NonregulatedSegmentEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" name="NonregulatedSegmentEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_NonregulatedSegmentMember" name="NonregulatedSegmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_NumberOfCustomersDiscontinuedOperations" name="NumberOfCustomersDiscontinuedOperations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="ato_NumberOfCustomersNaturalGasDistribution" name="NumberOfCustomersNaturalGasDistribution" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="ato_NumberOfDivisionsNaturalGasDistribution" name="NumberOfDivisionsNaturalGasDistribution" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_OperatingRevenuesAndPurchasedGasCostLineItems" name="OperatingRevenuesAndPurchasedGasCostLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_OtherAbstract" name="OtherAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeLossCommodityCashFlowHedgesNetOfTax" name="OtherComprehensiveIncomeLossCommodityCashFlowHedgesNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeReclassificationAdjustmentAndUnrealizedGainLossOnDerivativesIncludedInNetIncomeAndArisingDuringPeriodNetOfTax" name="OtherComprehensiveIncomeReclassificationAdjustmentAndUnrealizedGainLossOnDerivativesIncludedInNetIncomeAndArisingDuringPeriodNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeReclassificationAdjustmentAndUnrealizedGainLossOnDerivativesIncludedInNetIncomeAndArisingDuringPeriodTax" name="OtherComprehensiveIncomeReclassificationAdjustmentAndUnrealizedGainLossOnDerivativesIncludedInNetIncomeAndArisingDuringPeriodTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeReclassificationAdjustmentOnForwardCommodityContractsIncludedInNetIncomeNetOfTax" name="OtherComprehensiveIncomeReclassificationAdjustmentOnForwardCommodityContractsIncludedInNetIncomeNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeReclassificationAdjustmentOnTreasuryLocksIncludedInNetIncomeNetOfTax" name="OtherComprehensiveIncomeReclassificationAdjustmentOnTreasuryLocksIncludedInNetIncomeNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeUnrealizedGainLossOnForwardCommodityContractsArisingDuringPeriodNetOfTax" name="OtherComprehensiveIncomeUnrealizedGainLossOnForwardCommodityContractsArisingDuringPeriodNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="ato_OtherComprehensiveIncomeUnrealizedGainLossOnTreasuryLocksArisingDuringPeriodNetOfTax" name="OtherComprehensiveIncomeUnrealizedGainLossOnTreasuryLocksArisingDuringPeriodNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_PensionAndPostretirementBenefitCostsMember" name="PensionAndPostretirementBenefitCostsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_PurchaseCommitmentAmountMaximum" name="PurchaseCommitmentAmountMaximum" nillable="true" substitutionGroup="xbrli:item" type="us-types:perUnitItemType" xbrli:periodType="instant" />
  <xsd:element id="ato_PurchaseCommitmentAmountMinimum" name="PurchaseCommitmentAmountMinimum" nillable="true" substitutionGroup="xbrli:item" type="us-types:perUnitItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_RateCaseCostsMember" name="RateCaseCostsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_RatioOfTotalDebtToTotalCapital" name="RatioOfTotalDebtToTotalCapital" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_RecoverableLossOnReacquiredDebtMember" name="RecoverableLossOnReacquiredDebtMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_RegulatedFacilitiesMember" name="RegulatedFacilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_RegulatedOperationsLineOfCreditFacilitiesCovenantTerms" name="RegulatedOperationsLineOfCreditFacilitiesCovenantTerms" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_RegulatedSegmentsEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" name="RegulatedSegmentsEffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_RegulatedTransmissionAndStorageSegmentMember" name="RegulatedTransmissionAndStorageSegmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_RegulatoryAssetFutureRecoverablePensionCosts" name="RegulatoryAssetFutureRecoverablePensionCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="ato_RegulatoryAssetsAndLiabilitiesTableAbstract" name="RegulatoryAssetsAndLiabilitiesTableAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_RegulatoryCostOfRemovalAssetMember" name="RegulatoryCostOfRemovalAssetMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_RegulatoryCostOfRemovalLiability" name="RegulatoryCostOfRemovalLiability" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_RegulatoryCostOfRemovalObligation" name="RegulatoryCostOfRemovalObligation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_ScheduleOfCommodityDerivativeVolumesTableTextBlock" name="ScheduleOfCommodityDerivativeVolumesTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_ScheduleOfExpectedDeferredGainsLossesRecognitionTableTextBlock" name="ScheduleOfExpectedDeferredGainsLossesRecognitionTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_ScheduleOfOperatingRevenuesAndPurchasedGasCostBySegmentTable" name="ScheduleOfOperatingRevenuesAndPurchasedGasCostBySegmentTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_ScheduleOfOtherFairValueMeasuresTableTextBlock" name="ScheduleOfOtherFairValueMeasuresTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_ScheduleOfRegulatoryAssetsAndLiabilitiesTableTextBlock" name="ScheduleOfRegulatoryAssetsAndLiabilitiesTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_SecondFacilityRegulatedOperationsMember" name="SecondFacilityRegulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_SegmentReportingInformationBalanceSheetAbstract" name="SegmentReportingInformationBalanceSheetAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_SegmentReportingInformationOtherCurrentAssets" name="SegmentReportingInformationOtherCurrentAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="ato_SegmentReportingInformationOtherCurrentLiabilities" name="SegmentReportingInformationOtherCurrentLiabilities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_SegmentReportingInformationOtherNoncurrentAssets" name="SegmentReportingInformationOtherNoncurrentAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="ato_SegmentReportingInformationOtherNoncurrentLiabilities" name="SegmentReportingInformationOtherNoncurrentLiabilities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="ato_SharesIssuedAtOverallotmentOption" name="SharesIssuedAtOverallotmentOption" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_SignificantPurchaseCommitmentAmount" name="SignificantPurchaseCommitmentAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_Texas8209Member" name="Texas8209Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_ThereafterMember" name="ThereafterMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_ThirdFacilityRegulatedOperationsMember" name="ThirdFacilityRegulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_TotalHedgeGainLossReclassifiedToEarnings" name="TotalHedgeGainLossReclassifiedToEarnings" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UncommittedFacilityNonregulatedOperationsMember" name="UncommittedFacilityNonregulatedOperationsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="ato_UndistributedEarningsFromDiscontinuedOperationsAllocatedToParticipatingSecurities" name="UndistributedEarningsFromDiscontinuedOperationsAllocatedToParticipatingSecurities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredDebenturesDue2028Member" name="UnsecuredDebenturesDue2028Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredSeniorNotesDue2014Member" name="UnsecuredSeniorNotesDue2014Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredSeniorNotesDue2017Member" name="UnsecuredSeniorNotesDue2017Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredSeniorNotesDue2019Member" name="UnsecuredSeniorNotesDue2019Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredSeniorNotesDue2034Member" name="UnsecuredSeniorNotesDue2034Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredSeniorNotesDue2041Member" name="UnsecuredSeniorNotesDue2041Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="ato_UnsecuredSeniorNotesDue2043Member" name="UnsecuredSeniorNotesDue2043Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>


