2 a There are five gases named in the passage. Write down whether each one
is an element or a compound.
b Which gas in the air exists as single atoms? Draw a particle diagram to
illustrate the way that the particles are arranged in this gas.
c Name a gas in the air which is an element made from molecules
containing two atoms. Draw a particle diagram to illustrate the way that
the atoms and molecules are arranged in this gas.
d Name a gas in the air which is a chemical compound. Draw a particle
diagram to illustrate the way that the atoms and molecules are arranged
in this gas.
e If you had some air which contained a million molecules in total, how
many of these molecules would be:
i argon
ii carbon dioxide?