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

Write the chemical formulae for the following substances and calculate the molecular mass for each one of them:
$(a)$ Caustic potash
$(b)$ Baking soda
$(c)$ Limestone
$(d)$ Caustic soda
$(e)$ Ethanol
$(f)$ Common salt

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

Which of the following statements is not true about an atom?

Write the chemical formulae for the following compounds and find the ratio by mass of the combining elements in each one of them.
$(N=14 \ u, H=1 \ u, C=12 \ u, O=16 \ u, S=32 \ u)$
$(a)$ Methane
$(b)$ Carbon dioxide
$(c)$ Hydrogen sulphide

$(a)$ 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 $NO_{3}^{-}$