JEE Main Rank Booster 2021
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These are the steps:-
1. write the atomic number.
2 write the electronic configuration.
3. check last subshells
4 combo - a. [(n-1)d, ns] b. [(n) s, np ] c. [(n-1) d, ns, (n-2) f] d. [(n) s,]
these will be valencies.