Question

b. 6 e. 32 a. 2 c. 10 d. 14 31. Place the following ions in order of increasing radius: Ali, F, Mg2., and N3. a. F< Mg2+ < N3- < Al 3+ b. F <N3- <A13+ < Mg2+ c. F< N3- < Mg2+ < Al 3+ d. N3- <F. < Mg2+ < Al 3+ e. Al 3+ < Mg2+ < F< N3- 32. Place the following atoms in order of increasing ionization energy C, N, and Si a. C<N< Si b. C<si<N C. Si<C<N d. Si <N<C e. N<C<Si 38. What is the ground state electron configuration of 25Mn? a. 1s22s22p63s23p63d64s b. 1s 2s22p63s23p63d5452 c. 1s 2s22p 3s23p 3d7 d. 1s 2s22p63s 3p63d5 e. 1s 2s22p03s 3p64s24d5

Answer 1

31.

The ions present here are isoelectronic. So, the only variable thing is effective nuclear charge. For cations, nuclear charge is always more than that in neutral state, so eventually radii is smaller. Al³⁺ has 3 electrons less than what it should have, So, the effective nuclear charge is maximum on the outer shell electrons. Mg²⁺ has 2 less than what it should have, so, radius of it is slightly greater than that of Mg²⁺. For anion, nuclei have to attract more electrons than it does in neutral molecule, so effective nuclear charge on outer shell electrons are lower than that in neutral state. So, due to the same reason, N^3- will have higher radii than F^-. So, ionic radii order is: Al³⁺ < Mg²⁺ < F^- < N^3- (e).

32.

Ionisation energy depends on several things, but only important things are two:

• Electronic configuration
• Radius

We know half filled and fully filled electronic configurations are more stable than others. Here, N has such an electronic configuration: 1s²2s²2p³. So, ionisation energy will be highest for N. Next comes C and Si, both having similar type of electronic configuration: ns²np⁴. Now, since radii of Si is higher, so it has less attraction of nuclei on the outer shell eletrons. So, ionisation energy is less for Si than C. So, order is : Si < C < N (c).

38.

Electronic configuration of ₂₅Mn is: 1s²2s²2p⁶3s²3p⁶3d⁵4s² (b).

The reason why 3d⁵ configuration is observed is the stability of half filled electronic shell. There are 5 d-orbitals. So, this configuration is the ground state electronic configuration due to having lowest energy.