New
New
Year 10
AQA
Higher

# Atomic number and mass number

I can relate the atomic number and mass number to the structure of atoms of each element.

New
New
Year 10
AQA
Higher

# Atomic number and mass number

I can relate the atomic number and mass number to the structure of atoms of each element.

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## Lesson details

### Key learning points

1. The atomic number of an element states the number of protons in the nucleus of every atom of that element.
2. The number of electrons in an atom is equal to the number of protons in the nucleus of the atom.
3. The mass number of an element is about equal to the number of protons and neutrons in atoms of that element.

### Common misconception

Pupils often mix up the atomic number and atomic mass number and get confused over which subatomic particles these represent.

It helps to describe the atomic number as the proton number to help the pupils remember. Also, the provided periodic tables often have a key to help and this should be highlight to pupils.

### Keywords

• Atomic number - Gives the number of protons in the nucleus of an atom.

• Mass number - Is the total number of protons and neutrons in the nucleus of an atom.

• Relative atomic mass - Is the mean mass of an atom relative to 1/12th the mass of an atom of carbon-12.

It pays to practise the skill of determining the number of subatomic particles for different elements as much as possible. Pupils forget and will keep confusing the atomic and mass numbers.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
On the periodic table, what does the number 9 represent for the element Fluorine?
atomic mass
Correct answer: atomic number
group number
period number
Q2.
Match the element to its correct atomic number.

8

6

10

16

20

12

Q3.
Which of the following elements are in group 3?
sodium
yttrium
scandium
Q4.
The element with the atomic number 26 is known for its use in construction due to its strength and low density. What is this element?
Correct Answer: iron, Fe
Q5.
Give the name, or symbol, of an element in the first period on the periodic table.
Correct Answer: hydrogen, H, Helium, He
Q6.
The position of an element in the periodic table is linked to its arrangement of electrons and to its atomic number.
False

## Exit quiz

### 6 Questions

Q1.
What does the atomic number of an element indicate?
the number of neutrons
Correct answer: the number of protons
the total number of protons and neutrons
Correct answer: the number of electrons in a neutral atom
Q2.
True or false? The atomic number is equal to the number of electrons in a neutral atom.
False
Q3.
What is the relative atomic mass?
the mass of protons
the mass of neutrons
the total mass of an atom
Correct answer: the average mass of an atom compared to carbon-12
the total number of protons and neutrons in the nucleus of an atom
Q4.
If an atom has an atomic number of 6, how many electrons does it have?
Correct Answer: 6, six
Q5.
How does the mass number differ from the atomic number?
mass number includes electrons
mass number is only about protons
Correct answer: mass number includes protons and neutrons
there is no difference
Q6.
An element has a mass number of 23 and an atomic number of 11. How many neutrons does it have?
Correct Answer: 12, twelve