Question

1)The metals of group 2 from top to bottom are: Be, Mg, Ca, Sr,Ba. Which if these metal will form ions most readily and why?

Answer 1

1) Most ionizable atom

Atomic size increases as you go down a Group (see image 1). We are adding electrons to increasingly larger shells.

The valence electrons are further from the attraction of the nucleus, so they are less tightly held.

Thus, Ba will form ions most readily.

2) Ionization energy

As an atom gets larger, the electrons are less strongly attracted to the nucleus, so it takes less energy to remove the valence electrons.

Ionization energies decrease from top to bottom of a Group in the Periodic Table.

Thus, in Group 2, Be has the highest ionization energy, and it decreases as you go down the Group. Ba has the lowest ionization energy.

3) Ionization energy exceptions

In general, ionization energies increase from left to right in a period.

However, the ionization energies of B and O are smaller than that of their immediate predecessors (see image 2).

The ionization energy of B is less than that of Be because B has a filled 2s orbital, which increases the shielding of the 2p electron and reduces the ionization energy.

The ionization energy of O is less than that of N because we are adding an extra electron to a half-filled 2p subshell.

The extra electron must go into an orbital that already contains another electron. The increased repulsion raises the energy level.

It becomes easier to remove an electron, so the ionization energy decreases.