how does ionization energy vary across a period? within a family or group?

Answer 1

FOR 1st IONIZATION ENERGIES.

Simply put: On the Periodic Table, Ionization energies INCREASE from Left to Right across Periods, and DECREASE from Top to Bottom in a Group.

Giving some thought the the Electron structure of the atoms, we see that elements at the top have their valence shell closer to the nucleus, while those at the bottom have their valence shells farther away from the nucleus.

As you move from left to right across a period the valence shell fills up with more electrons, so there is more negative charge to be pulled close to the nucleus by the positive nuclear charge, but the distance of the whole shell is still the same (Remeber Coloumbs Law! F = Q1*Q2/distance squared).

This all comes down to Bigger atoms with their valence shell far away that have a low number of electrons in that shell, have lower Ionization energies. While Smaller atoms with their valence shell closer, and having high number of electrons, have higher Ionization energies (joules needed to strip electrons).

Answer 2

down the group ionization energy decrease as number of orbitals increase this refer to low attraction between nucleus and outer shell so energy required to remove one or more electron(ionization energy) decrease