Look at the relative positions of each pair of atoms

Solution:

Here we have to find out the number of core and valence electrons present in each pair of atoms listed here.

The listed atoms are

a. carbon and silicon c. nitrogen and phosphorus

b. oxygen and sulfur d. magnesium and calcium

Core electrons:- The electrons present in the inner shell of an atom is called as core electron .

Valence electron :-The electrons present in the outermost shell or valence shell of an atom is called as valence electrons.

For example: Let us consider Li-atom

The atomic number of Li is 3, thus the electronic configuration is

3Li - 1s2 2s1

Here 1s2 is core shell and it contain 2 electrons

2s1 is the valence or outermost shell it contain 1 electron.

Step 1

a. Carbon (C) and Silicon (Si)

In order to find out the core and valence electrons present in C and Si-atom, we have to draw the electronic configuration.

6C: 1s22s22p2:- Her 1s is the core shell contain 2 electron and 2s, 2p are the valence shell contain 4 electrons.

14Si: 1s2 2s2 2p6 3s23p2:- Here the core shell contain 10 electrons (1s2 2s2 2p6) and the valence shell contain 4 electrons (3s2 and 3p2).