Page 59 - 新思维科学学生用书7 样章

2 Materials and their structure

Questions

7 Which three elements are combined in calcium nitrate?
8 Which three elements are combined in magnesium carbonate?
9 Which three elements are combined in lithium sulfate?

Sometimes, the name of a compound tells you how many of each kind of atom are bonded together.

O C O C O

A particle of carbon dioxide A particle of carbon monoxide

Carbon dioxide particles are made up of one carbon atom joined to two oxygen atoms. ‘Di’ means two.

Carbon monoxide particles are made up of one carbon atom joined to one oxygen atom. ‘Mon’ or
‘mono’ means one.

Particle diagrams

Particle diagrams, like those for carbon dioxide and carbon monoxide, show which atoms of which
elements make up the particle.

It is easy to decide if a substance is a compound by looking at the particle diagram. If there are different

kinds of atom bonded together, then it is a compound.

H H
C

O C O H O H O O H H

A particle of carbon A particle of water, A particle of A particle of
dioxide, CO 2 H O oxygen, O methane, CH 4
2
2
Carbon dioxide, water and methane are all compounds because their particles are made up of different
kinds of atom. Oxygen is an element because the atoms in the particle are both oxygen atoms.

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