1. GCSE Chemistry Unit 1: Chemistry 1 AQA Specification
C1.1 Fundamental ideas in chemistry
C1.1.1 Atoms

2. 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

3. 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

4. The Atom
The electrical charge of each particle can be written in a ‘relative electrical charge’ table
Name of particle
Charge
Proton
+1 (positive)
Neutron
0 (neutral)
Electron
-1 (negative)

5. Elements carbon Atoms can have different numbers of particles
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

6. Elements oxygen If we add two more of each particle… Two more 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

7. Elements sodium If we add even more particles… Three more 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

8. 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

9. Particles
carbon
oxygen
sodium
– – – – – –
6 protons
6 electrons
8 protons
8 electrons
11 protons
11 electrons
Sodium has eleven protons in the nucleus, therefore it has eleven electrons flying around the outside
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
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

10. 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 second can hold up to 8.
The third can also hold up to 8.

11. 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

12. 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

13. 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

14. 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: = 11

15. 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

16. Drawing elements
There are two electrons on the first energy level and four on the second energy level
carbon
oxygen
sodium
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

17. 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

18. 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’