Question

Element X is the first element of alkaline earth metals family. An element Y is the first element of alkali metals family. An element Z is the first element of the halogen family. Among the three elements which one has a larger atomic size?

• A. Element X
• B. Element Y
• C. Element Z
• D. All three have the same size

Answer 1

The correct option is B Element Y

The first element of alkali metals family is lithium. The first element of alkaline earth metals family is beryllium. The first element of the halogen family is fluorine. Beryllium, lithium and fluorine belong to the same period.
In a period on moving from left to right, the effective nuclear charge increases, the force of attraction on the outermost electrons increases and consequently the size of the atom decreases. Among the given elements, element Y i.e., lithium has the largest atomic size.