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AQA Specification. GCSE Chemistry. Unit 1: Chemistry 1. C1.1 Fundamental ideas in chemistry. C1.1.1 Atoms. The Atom. An atom consists of three main particles. Protons, which are positively charged. Nucleus. Neutrons, which have no charge. Electrons, which are negatively charged.

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slide1

AQA Specification

GCSE Chemistry

Unit 1: Chemistry 1

C1.1 Fundamental ideas in chemistry

C1.1.1 Atoms

slide2

The Atom

An atom consists of three main particles

Protons, which are positively charged

Nucleus

Neutrons, which have no charge

Electrons, which are negatively charged

slide3

The Atom

orbital

The electrons constantly fly around the nucleus

The orbital shows us where we are most likely to find the electrons at any given moment in time

slide4

The Atom

The electrical charge of each particle can be written in a ‘relative electrical charge’ table

slide5

Elements

carbon

6 protons

6 neutrons

6 electrons

Atoms can have different numbers of particles

If an atom has six protons,

six neutrons

and six electrons,

it is a carbon atom.

Carbon is an element

slide6

Elements

oxygen

8 protons

8 neutrons

8 electrons

If we add two more of each particle…

Two more protons

This is an oxygen atom

Two more neutrons

Oxygen is a different element to carbon

Two more electrons

slide7

Elements

sodium

11 protons

12 neutrons

11 electrons

If we add even more particles…

Three more protons

This is a sodium atom

Four more neutrons

Sodium is a different element to carbon and oxygen

Three more electrons

slide8

Particles

So the three particles which make up an atom are the protons, electrons and neutrons

The number of protons is always the same as the number of electrons in an atom

slide9

Particles

carbon

oxygen

sodium

+ + + + + +

– – – – – –

6 protons

6 electrons

8 protons

8 electrons

11 protons

11 electrons

Carbon has six protons in the nucleus, therefore it has six electrons flying around the outside

Oxygen has eight protons in the nucleus, therefore it has eight electrons flying around the outside

Sodium has eleven protons in the nucleus, therefore it has eleven electrons flying around the outside

Electrons are negative, and protons and positive. If you have the same number of positive and negative particles, you have no overall charge

So we can say that atoms have no overall electric charge

slide10

Orbitals

1st orbital

2nd orbital

3rd orbital

You may have noticed some atoms have more orbitals

Each orbital can only hold a certain number of electrons

The first orbital can hold up to 2.

The third can also hold up to 8.

The second can hold up to 8.

slide11

Orbitals

1st orbital

2nd orbital

3rd orbital

So the more electrons an atom contains, the more orbitals it needs to house them all

Orbitals can also be known as shells or energy levels

slide12

Drawing elements

If you are asked to draw an element, firstly you need to find out how many electrons it has. Let’s take sodium for example

We know it has 11 electrons in its orbitals

slide13

Drawing elements

When you draw elements yourself you won’t need to draw the protons and neutrons, so the nucleus can be drawn as a circle in the centre

Then you need to draw the orbitals. Don’t forget how many electrons can fit on each one. 2, 8, 8

slide14

Drawing elements

You can draw electrons as a cross and it’s also best to draw them in pairs

X

X

X

X

X

X

X

X

X

X

X

For sodium you need a total of 11 electrons.

That means two on the first shell

Eight on the second shell

And just one on the third shell: 2+8+1 = 11

slide15

Drawing elements

X

X

X

X

X

X

X

X

X

X

X

X

X

X

carbon

oxygen

So, carbon would be drawn like this, with six electrons

And oxygen like this, with eight electrons

slide16

Drawing elements

There are two electrons on the first energy level and four on the second energy level

sodium

carbon

oxygen

2, 4

2, 6

2, 8, 1

In addition to drawing the elements you could also describe the electronic structure underneath by saying how many electrons there are on each energy level

slide17

Element names

There are around 100 known elements in the universe and each one is represented by a ‘chemical symbol’

The chemical symbol is made up of one, two or sometimes three letters.

The first letter is always a capital, and any other letters are written in lowercase

slide18

Element names

carbon

oxygen

sodium

C

O

Na

The chemical symbols come from the Latin word for the element. Sometimes the Latin word is similar to the English word so you can easily guess the element.

Carbon is ‘C’ and oxygen is ‘O’

However, if we look at sodium, the Latin word for this element is ‘natrium’ so the chemical symbol is ‘Na’