Question

1.* Write electron configurations for the 2 + 2 plus cations of these elements.

a.Fe
b.Co
c.Ni
2.Write electron configurations for the 3 + 3 plus cations of these elements.

a.chromium
b.manganese
c.iron
3. Write the symbol for the ion formed when each element gains electrons and attains a noble-gas electron configuration.

a.Br
b.H
c.As
d.Se
4.* Write electron configurations for the following atoms and ions, and comment on the result.

Ar
Cl − cap cl to the minus
S 2 − cap s super 2 minus end super
P 3 −

Answer 1

1.

`a.\  Fe^(2+): 1 s^(2) 2 s^(2) 2 p^(6) 3 s^(2) 3 p^(6) 4s 3d^(5) \ or \ [Ar]4s 3d^(5)`


`b.\ Co^(2+): 1 s^(2) 2 s^(2) 2 p^(6) 3 s^(2) 3 p^(6) 4s^(2) 3d^(5) \ or \ [Ar]4s^(2) 3d^(5)`


`c.\ Ni^(2+): 1 s^(2) 2 s^(2) 2 p^(6) 3 s^(2) 3 p^(6) 4s^(2) 3d^(6) \ or \ [Ar]4s^(2) 3d^(6)`

2.

`a.\ Cr^(3+): 1 s^(2) 2 s^(2) 2 p^(6) 3 s^(2) 3 p^(6) 4s^(2) 3d \ or \ [Ar]4s^(2) 3d`


`b.\ Mg^(3+): 1 s^(2) 2 s^(2) 2 p^(5)`


`c.\ Fe^(3+): 1 s^(2) 2 s^(2) 2 p^(6) 3 s^(2) 3 p^(6) 4s^(2) 3d^(3) \ or \ [Ar]4s^(2) 3d^(3)`

3.

`a. \ Br^(-)`


`b. \ H^(-)`


`c.\ As^(3-)`


`d.\ Se^(2-)`

4. Argon is a noble gas so it is stable. Ar, Cl-, S2- and P3- are all anions that give excess electrons to become stable like the nearest noble gas, which is in this case, Argon. So, all of these have the same electronic configuration:


`1 s^(2) 2 s^(2) 2 p^(6) 3 s^(2) 3 p^(6)`