M shell of two elements A and B have 18 electrons each. The difference in the number of electrons present in N shell of A and B is 8. M shell is the penultimate shell in B. Predict the range of probable atomic numbers of A and B.

M shell of two elements A and B have 18 electrons each. The difference

1.	M shell of two elements A and B have 18 electrons each. The difference in the number of electrons present in N shell of A and B is 8. M shell is the penultimate shell in B. Predict the range of probable atomic numbers of A and B.
Answer» Solution :As the penultimate SHELL of B is M shell which POSSESSES 18 ELECTRONS the valence shell should be N shell. The possible electronic configuration fo B ranges from 2,8,18, 1 to 2,8 , 18,8 The atomic numbers of B may range from Z=29 to Z =36. The electronic arrangement of A corresponding to the RESPECTIVE arrangement of B ranges from 2,8,18,9,2 to 2,8,18,16 , 2 . The atomic number of A may range from Z =39 to Z=46.