Which of the following statements is correct?

• A
  The $X^{-}$ ion is larger in size than the $X$ atom.
• B
  The $X^{+}$ ion is larger in size than the $X$ atom.
• C
  The $X^{+}$ and $X^{-}$ ions are equal in size.
• D
  The $X^{+}$ ion is larger in size than the $X^{+}$ ion.