In order to be treated as alimony (and be deductible on your tax return), payments made you made to your ex-spouse) must meet all these requirements:
Please see for reference IRS publication 504, Divorced or Separated Individuals - http://www.irs.gov/pub/irs-pdf/p504.pdf
If part of the mortgage interest was paid by you of from jointly owned funds - you are entitled to claim that expenses on you r tax return.
You a child lived with you more than half of the year - you may claim that child as a dependent. In this situation if you paid more than half the cost of keeping up your
and if you lived apart from your spouse during the last 6 months of the tax year - you would be considered unmarried for tax purposes and may use a head of household status.