AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Hodder Education Revision Lessons

The fundamental ideas in Chemistry

Fundamental ideas in chemistry

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Overview

• Atoms and elements are the building blocks of chemistry.• Atoms contain protons, neutrons and electrons. • When elements react they produce compounds.

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Elements

All substances are made of atoms.

A substance that is made of only one sort of atom is called an element.

There are over 100 different elements.

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

The periodic table 1

Elements are shown in the periodic table (see the next slide).

The groups contain elements with similar properties.

What are the properties of:

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• the group 1 elements?• the group 7 elements?

AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

The periodic table 2

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Chemical symbols

Atoms of each element are represented by a chemical symbol. For example, O represents an atom of oxygen and Na represents an atom of sodium.

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What are the symbols for: • carbon• magnesium• calcium• helium

AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Atoms 1

Atoms have a small central nucleus, which is made up of protons and neutrons and around which there are electrons.

The relative electrical charges are:

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Name of particle Charge

Proton +1

Neutron 0

Electron –1

AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Atoms 2

The number of electrons in an atom is equal to the number of protons in the nucleus.

Atoms have no overall electrical charge.

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Atomic number and mass number 1

All atoms of a particular element have the same number of protons.

Atoms of different elements have different numbers of protons.

The number of protons in an atom of an element is its atomic number. The sum of the protons and neutrons in an atom is its mass number.

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

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Atomic number and mass number 2

How many protons and neutrons do these elements have?

He

C

C

O

Fe

4

2

12

6

13

6

16

8

56

26

AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Shells and energy levelsElectrons occupy particular energy levels.

Each electron in an atom is at a particular energy level (in a particular shell).

The electrons in an atom occupy the lowest available energy levels (innermost available shells).

The shells fill in the order 2, 8, 8 ...

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AQA GCSE Science & Additional Science

Chemistry 1 Topic 1

Electron structure

The noble gases are unreactive because their outer shells are full.

1

1Draw the electron structures for H, Li, O and Cl.7

3

16

8

35

17