Statement 1: ₄Be, ₉F belong to the same period and ₉F is bigger in size.

Statement 2: ₄Be, ₉F belong to the same period and ₄Be is bigger in size.

Statement 3: ₁₉K, ₂₀Ca belong to the same period and ₁₉K is bigger in size.

Statement 4: ₁₉K, ₂₀Ca belong to the same period and ₂₀Ca is bigger in size.

Which of the following statements is correct?

Both ₄Be and ₉F belong to the same period 2 and Be is bigger in size. Whereas, both ₁₉K and ₂₀Ca belong to the same period 4 and ₁₉K is bigger in size.
Electronic configuration of Be = 2, 2
Electronic configuration of F = 2, 7
In Be and F, electrons are filled in 2 shells. So, they both belong to the 2nd period.

Atomic size decreases across a period from left to right, so Be is bigger than F. 
Electronic configuration of K = 2, 8, 8, 1
Electronic configuration of Ca = 2, 8, 8, 2
In K and Ca, electrons are filled in 4 shells. So, they both belong to the 4th period. But, as we know, atomic size decreases across a period from left to right, so K is bigger than Ca.