Answer:
Part A:
Order: K<Rb<Cs
Part B:
Order: O<C<Be
Part C:
Order:CL<S<K
Part D:
Order:Mg<Ca<K
Explanation:
Atomic Size:
It is the distance from the center to atom to the valance shell electron. It is very difficult to measure the atomic size because there is definite boundary of atom.
Trend:
Moving from top to bottom in a group, Atomic Size increases.
Moving from left to right in a period, Atomic size generally decreases.
On the basis of above trend we will solve our question:
Part A:
All elements belong to Group 1:
Moving from top to bottom in a group, Atomic Size increases.
Order: K<Rb<Cs
Part B:
All elements belong to 2nd Period:
Moving from left to right in a period, Atomic size generally decreases.
Order: O<C<Be
Part C:
S belongs to 3rd Period, K, Cl belong to 4th period
Order:CL<S<K
Part D:
Mg is above Ca in group 2 and K is before Ca in 4th period
From trends described above:
Order:Mg<Ca<K
