29)
a. Looking at the trends in first ioniaztion energies across period 3, there is a sudden unusual dip with Al and S. First ionization energy is the energy required to remove the first electron from an atom. This means that it is much easier to remove an electron from S than it is to remove one from Al, because the extra electron in the p shell of S repels the other electron, making it much easier to remove.
b. Electronegativity is the ability of an atom to attract another electron. Electronegativity increases across the groups and decreases down the periods, which makes the halogens the most electronegative group. The noble gases have an electronegativity of zero, because all of their electron shells are filled, and they don't want to attract another electron.
c. Atomic radius is the average distance to the nucleus of the atom from the edge of its surrounding electron cloud. Oxygen would have the smallest atomic radius becuse atomic adius increases down the periods, but decreases across the groups.
