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Q. How can I learn the valencies of the first 20 elements?
Answer: As a result, the periodic table’s initial twenty elements begin with H and ending with Ca. Forming a bond with the no. of the group the element is placed in is the simplest approach to remembering the no. of valence electrons.
I’m going to skip noble gases because they have a steady octet and are rarely engaged in chemical reactions.
Beginning with the second row, write: Group 1 – Li – has one valence electron (v.e);
Group 2 – Be – has two v.e;
Group 13 – B – has three v.e;
Group 14 – C – has four v.e;
Group 15 – N – has five v.e;
Group 16 – O – has six v.e;
Group 17 – F – has seven v.e;
Because the first twenty elements are not found in groups 3-12, the group number jumps from 2 to 13.
The pattern then repeats in the third row. Again,
Group 1 (Na) has one v.e.,
Group 2 (Mg) has two v.e.,
Group 13 (Al) has three v.e.,
Group 14 (Si) has four v.e., and so on.
So, if you can look at a periodic table, you can figure out how many valence electrons there are by looking at the group number.
The number of valence electrons is equal to the digit that denotes the units (1 in 1, 3 in 13, 4 in 14, 6 in 16, and so on).
So, always think group number→units digit→ valence electrons.
