Three elements X , Y and Z have atomic numbers 19 , 37 and 55 respectively . Then the correct statements (s) is / are

Options

A. Their ionization potential would increase with increasing atomic number
B. Y' would have an ionisation potential between those of 'X' and 'Z'
C. Z' would have the highest ionization potential
D. Y' would have the highest ionization potential

Answer

B

Explanation

Elements X,Y,Z with atomic numbers `19,37,55` lie in group `1` (alkali metals). On moving down a group from the size of atoms increases, the outermost electrons become less strongly held. So the ionization energy decreases. Therefore, IE of Y could be betwwen those of X and Z.
`{:(X,Y,Z):}`
`{:(K(19),Rb(37),Cs(55)):}`
`{:(I.E.,4.3,4.2,3.9):}`