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Covalent Bonding Practice Questions

Question 1

4 marks

Covalent bonding joins atoms of non-metal elements together to form molecules.

(a)

Which substance is made up of molecules in which the atoms are joined by covalent bonds?

Put a cross ( ☒ ) in the box next to your answer.

☐ A calcium oxide, CaO\mathrm{CaO}

☐ B nitrogen, N2\mathrm{N_2}

☐ C potassium, K\mathrm{K}

☐ D lithium fluoride, LiF\mathrm{LiF}

(b)

Draw a dot and cross diagram for a molecule of hydrogen, H2\mathrm{H_2}.

(c)

Draw a dot and cross diagram for a molecule of hydrogen chloride, HCl\mathrm{HCl}.

Show outer electrons only.

Question 2

3 marks

Scientists use models to compare the sizes of atoms and small molecules.

(a)

Which of these is the order of magnitude of the diameter of a typical atom?

Put a cross ( ☒ ) in the box next to your answer.

☐ A 10−5 m10^{-5}\ \mathrm{m}

☐ B 10−8 m10^{-8}\ \mathrm{m}

☐ C 10−10 m10^{-10}\ \mathrm{m}

☐ D 10−15 m10^{-15}\ \mathrm{m}

(b)

A molecule of water has a diameter of about 2.8×10−10 m2.8 \times 10^{-10}\ \mathrm{m}.

Calculate the number of water molecules that would have to be placed side by side in a straight line to stretch a distance of 1 mm1\ \mathrm{mm}.

Give your answer in standard form.