Name the anion and cation which constitute the molecule of aluminium oxide.

Which of the following species have $18$ electrons? $Ca^{2+}, K^{+}, Na, Cl^{-}, Ar$. Also,state the reason why the chemical properties of all isotopes of an element are similar.

Write the chemical names of the following compounds:
$(a)$ $K_{2}SO_{4}$
$(b)$ $Mg_{3}(PO_{4})_{2}$
$(c)$ $NH_{4}Cl$
$(d)$ $ZnS$
$(e)$ $Na_{3}N$
$(f)$ $AgBr$

Calculate the number of moles in $60 \text{ g}$ of carbon. (in $\text{ moles}$)

Which of the following represents a correct chemical formula? Name it.

With a labelled diagram,describe an activity to demonstrate the law of conservation of mass.