Some of the elements and their atomic numbers are given in the table. (i) How many valence electrons are there in the element R ? (ii) What is the valency of P? (iii) Write the chemical formula of the compound formed by combining the elements P and Q.

Some of the elements and their atomic numbers are given in the table.

1.	Some of the elements and their atomic numbers are given in the table. (i) How many valence electrons are there in the element R ? (ii) What is the valency of P? (iii) Write the chemical formula of the compound formed by combining the elements P and Q.
Answer» <P> Solution :(i) Electronic configuration of R is : `{:(K,L,M),(2,8,3):}` Thus, there are 3 valence electrons in R. (ii) Electronic configuration of P is : `{:(K,L),(2,1):}` Therefore, VALENCY of P is one. (III) P has one electron and Q has 7 electrons in the valence shell. Therefore, formula of the compound will be PQ.