Question

how to get the valency of sodium and oxygen

Answer 1

To find the valency of sodium first write it's electronic configuration

Which is
2,8,1

For sodium to make an octet in it's outermost shell , it will be easy to lose 1 electron rather than gaining 7 . Hence , it's valency will be +1

Similarly, the Valency of oxygen will be 2-

Answer 2

To get the valence of sodium and oxygen we need to find out the atomic number

for example the atomic number of sodium is 11 show the electronic configuration will be 2,8,1.so the valency will be 1

similarly the atomic number of the oxygen is it so the electronic configuration will be 2,6 so to complete its octate state it will need 2 electronsshow the valency of the oxygen is 2.