posted by Anonymous .
Which one pair has the larger radius?Explain?
a. Calcium atom or calcium ion
b. Aluminum ion or Magnesium ion
Ca atom is 1s2 2s2 2p6 3s2 3p6 4s2
Ca^+2 = 1s2 2s2 2p6 3s2 3p6
The Ca ion is missing the last two electrons; wouldn't you expect the radius to be smaller?
Look at the electron configuration of Mg ion versus Al ion, then compare the nuclear charge of Al ion vs Mg ion on the pull of their outside electrons.