Question

1. Explain why the atomic radius of Ga is smaller than Ca. You cannot merely state the trend. You must

explain using Z and shielding.

2. Explain why the ionization energy of Ga is less than Ca.

3. Draw the best Lewis structures for the following species. Ensure you make the dots very clear to

see. Show nonzero formal charges on the correct atoms.

a) SbI4- anion

b) COCl2

c) XeOF4

4. For the above species, draw the molecular geometry showing and labelling bond angles and name

the molecular shape.

Answer 1

1) Because the electrons added in the transition elements are added in the inner electron shell and at the same time, the outer shell remains constant, the nucleus attracts the electrons inward. The electron configuration of the transition metals explains this phenomenon.

Well, in galium no of electrons are added up in the d orbitals. since the 4s and 4p electrons are not shielded off by the inner electrons, but yet the atomic no and hence the attractive force of nucleus increases. This results in the overall reduction in size compared to the Ca

Ga: 1s²,2s²,2p⁶,3s²,3p6,(3d¹⁰)*, 4s²,4p¹

Ca :1s²2s²2p⁶3s²3p⁶4s²

2) Gallium has one electron in the 4p orbital, which can be expelled to reveal a more stable and full 4s orbital. Calcium, however, has a fully stable 4s orbital as its valence orbital, which you would have to disrupt to take an electron away from

Gallium has a first ionization energy of 578.8 kJ/mol, and calcium has a first ionization energy of 589.8 kJ/mol .

3) and 4) see image