Which of the following species is electrically neutral and why?
$K^{+}, Cl^{-}, S^{2-}, P^{3-}, K$

State whether the following statement is true or false:
Oxygen molecules exist in the form of three molecules as $O_{2}$,$O_{3}$,and $O_{4}$.

As per the law of definite proportion,carbon and oxygen combine in the ratio of $3:8$. Compute the mass of oxygen gas that would be required to react completely with $15\,g$ of carbon.

$(a)$ What are molecules? Using examples, differentiate between the molecules of an element and a compound.
$(b)$ Derive the chemical formulae of the molecules formed between the following ions:
$(i)$ $Al^{3+}$ and $SO_{4}^{2-}$
$(ii)$ $Ba^{2+}$ and $NO_{3}^{-}$

The chemical formula of the chloride of a metal $M$ is $MCl$. Write the chemical formula of its oxide,bicarbonate,and sulphide.

What is the mass of one mole of oxygen atoms (in $g$)?