Question

For each atom in the table below, write down the subshell from which an electron would have to be removed to make a

−1

anion.

The first row has been completed for you.

atom

subshell from which electron removed to form

−1

anion

1s

Ca

Br

Answer 1

The electronic configuration of Ca( atomic number 20) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

An electron can be removed from the outer shell so that it can loosly bound by the nucleus to form positive ion.

But electron must be added to make it as a negative ion

Here electrom must be added to Ca for the next energy level that is 3d

Therefore the electronic configuration of Ca^- is ( which is actually impossible) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹

For Bromine

The electronic configuration of Br( atomic number 20) is [Ar] 3d¹⁰ 4s² 4p⁵

When one electron is added to 4p orbital it forms Br-

So its configuration is : [Ar] 3d¹⁰ 4s² 4p⁶