Question

1. Based on shielding explain why S2- is larger than S

2. O2- , F- , Ne, Na+ and Mg2+ are isoelectronic since they have the same number of electrons. Order them from largest to smallest in radius. Explain your reasoning.

3. In general, how do the following values change as one proceeds left to right on the periodic table:

a. Atomic radii

b. Ionization energy

c. Electron affinity

d. Metallic character

4. Write the following chemical equations:

a. Reaction associated with the first ionization energy of Fe

b. Reaction associated with the second ionization energy of Fe

c. Reaction associated with the electron affinity of Fe

d. Based on your answers to 6a and 6d, are ionization energy and electron affinities the reverse of one another?

Answer 1

Ans 1 :

The atomic number of sulfur is 16 , so it has 16 electrons when neutral. When it accepts two electrons , it becomes S^2- ion.

Now the two electrons add into the 3rd shell of the atom. There is an increase in the electron-electron repulsion and the shielding from the inner shells become insufficient for the increased number of electrons.

The effective nuclear charge on these electrons decrease due to reduction in proton: electron ratio.

So the size of S2- is more than the S.