Which of the following elements will form an acidic oxide?

Which of the following statements is not correct regarding the trends observed when moving from left to right across the periods of the Periodic Table?

Calcium is an element with atomic number $20$.
$(i)$ Will it be a metal or a non-metal?
$(ii)$ What will be its valency?
$(iii)$ What would be the formula of its chloride?
$(iv)$ Will it be larger or smaller than $K$ (Potassium)?

What would be the nature of oxides formed by the elements on the right-hand side of the periodic table?

Four elements $P, Q, R$ and $S$ have atomic numbers $12, 13, 14$ and $15$ respectively.
Answer the following questions giving reasons:
$(i)$ What is the valency of $Q$?
$(ii)$ Classify these elements as metals and non-metals.
$(iii)$ Which of these elements will form the most basic oxide?

The element with atomic number $14$ is hard and forms acidic oxide and a covalent halide. To which of the following categories does the element belong?