Question

Elements $X$, $Y$ and $Z$ have atomic numbers $19$, $37$ and $55$ respectively. Which of the following statements is true about them?

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

Answer 1

Answer: (B)

Y would have an ionization potential between those of X and Z.

Answer 2

Elements X, Y and Z with atomic numbers 19, 37, 55 lie in group 1 (alkali metals). Within a group, IE decreases from top to bottom. Therefore, IE of Y could be between those of X and Z.