Atoms, elements and compounds, Year 8: more practice

Hydrogen, sulfur and oxygen

HintMatch each capital letter to an element.

The whyH is hydrogen, S is sulfur and O is oxygen. The small number 2 tells you there are two hydrogen atoms.

One carbon atom and one oxygen atom

HintA missing number never means none.

The whyIf no number follows a symbol, there is just one atom of that element. CO is carbon monoxide.

Sodium chloride

HintThe name of the metal comes first, then the non-metal with its ending changed.

The whyTwo elements join, so the name of the second one ends in -ide: chlorine becomes chloride.

Potassium, sulfur and oxygen

HintThe ending -ate tells you about an extra element.

The whyNames ending in -ate hide oxygen. Potassium sulfate is made of potassium, sulfur and oxygen.

Copper sulfate

HintCompare the endings of the four names.

The whyThe others end in -ide and each has just two elements. Copper sulfate contains copper, sulfur and oxygen, which is why its name ends in -ate.

2

HintAn -ide ending tells you how many elements there are.

The whyThe ending -ide means a compound of just two elements. Here they are zinc and sulfur.

9

HintThe 3 in front multiplies the whole of H2O.

The whyOne H2O has two hydrogen atoms and one oxygen atom, which is 3 atoms. Three of them make 3 × 3 = 9.

An element

HintCount how many different kinds of circle there are.

The whyOnly one type of particle is present, so it is a single element. A compound would show different circles joined together.

A mixture

HintLook for any joins between the different circles.

The whyTwo substances are present but not chemically bonded, so it is a mixture of two elements.

Many

HintThink of the word 'polygon'.

The whyA polymer is made of many repeating small units joined in a long chain. Poly- is also in polygon and polythene.