Question

Easy way to learn valencies?

Answer 1

To find out valency (the tendency to lose or gain electron to obtain octet at the outer shell) you have to find out the number of valence electrons an element has.

You can find out the valence electrons of an element of know it's group number.

For non transition elements -

Group 1 - number of valance electron 1 ( valency one because it can lose 1 electron to obtain)Similiarly Group 2 elements - valency 2Group 13: 3 valence electronsGroup 14: 4 valence electronsGroup 15: 5 valence electronsGroup 16: 6 valence electronsGroup 17: 7 valence electronsGroup 18: 8 valence electrons (except for helium, which has 2)

For transition metals (group 3–12)

Group 3: 3 valence electronsGroup 4: 2 to 4 valence electronsGroup 5: 2 to 5 valence electronsGroup 6: 2 to 6 valence electronsGroup 7: 2 to 7 valence electronsGroup 8: 2 or 3 valence electronsGroup 9: 2 or 3 valence electronsGroup 10: 2 or 3 valence electronsGroup 11: 1 or 2 valence electronsGroup 12: 2 valence electron

You can also find out valency if you know its atomic number by using electronic configuration.

Example -

Atomic number of sodium = 11

Electronic configuration - 1s2, 2s2 2p6, 3s1

Since the last orbital has 1 electron it can easily lose its electron to obtain stable octet. Hence it's valency is 1.

Hope so it helps