New
New
Year 10
Edexcel
Foundation

# Isotopes

I can write and use the standard nuclear notation for different elements and their isotopes.

New
New
Year 10
Edexcel
Foundation

# Isotopes

I can write and use the standard nuclear notation for different elements and their isotopes.

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## Lesson details

### Key learning points

1. Atoms of many elements vary in the exact number of neutrons in their nucleus, and each version is called an isotope.
2. Existence of isotopes results in relative atomic masses of some elements not being whole numbers.
3. Standard nuclear notation shows the chemical symbol, the mass number and the atomic number of the isotope.

### Common misconception

Students often confuse the subatomic particle responsible for making an atom an isotope, and how isotopes are responsible for the relative atomic masses to 1 d.p.

Practice determining the number of neutrons in multiple isotopes.

### Keywords

• Isotope - An atom of an element with the same number of protons, but different mass numbers due to different numbers of neutrons.

• Proton - A subatomic particle found in the nucleus with a relative mass of 1 and a positive charge (+1).

• Neutron - A subatomic particle found in the nucleus with a relative mass of 1 and no charge.

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

Real world examples of the use of isotopes can help students to remember what they are.
Teacher tip

### Content guidance

• Contains subject matter which individuals may find upsetting.

### 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.
Which two subatomic particles are present in the nucleus of an atom?
electron
Q2.
The relative mass of a neutron is ...
Q3.
What is the mass number of an atom?
number of protons
Correct answer: total number of protons and neutrons
number of neutrons
total number of protons and electrons
number of electrons
Q4.
Order the method for working out the number of the three subatomic particles in an atom of sodium. Start with the number of protons, then work out the number of electrons, then finally neutrons.
1 - number of protons = atomic number or proton number, for sodium = 11
2 - number of electrons = same as the number of protons, for sodium = 11
3 - mass number = total number of protons + neutrons
4 - number of neutrons = mass number - number of protons, for sodium: 23 - 11 = 12
Q5.
Match the atoms with the number of neutrons in their nucleus. Use your periodic table to help.

7

10

20

22

4

8

Q6.
Chlorine atoms mainly exist as ³⁵Cl and ³⁷Cl. Why are the mass numbers different?
This is a mistake as they should all be the same.
³⁵Cl has 18 protons and ³⁷Cl has 20 protons.
³⁷Cl has gained two electrons to get a full outer shell.
³⁵Cl has 18 neutrons and ³⁷Cl has 20 protons.
Correct answer: ³⁵Cl has 18 neutrons and ³⁷Cl has 20 neutrons.

## Exit quiz

### 6 Questions

Q1.
Match the term to its definition.
Correct Answer:protons,subatomic particles with a mass of 1 and a positive charge

subatomic particles with a mass of 1 and a positive charge

Correct Answer:mass number,total number of protons and neutrons in an atom

total number of protons and neutrons in an atom

Correct Answer:isotopes,atoms of an element with different number of neutrons

atoms of an element with different number of neutrons

Correct Answer:neutrons,subatomic particles with a mass of 1 and no charge

subatomic particles with a mass of 1 and no charge

Q2.
The word 'abundance' is used to show the proportion of atoms of an element which are a particular isotope. It is often shown as a .
Q3.
Why do chlorine and copper have relative atomic masses which are not whole numbers i.e. 35.5Cl and 63.5Cu?
They contain half a proton.
They contain half a neutron.
They have lost half an electron.
They have gained half an electron.
Correct answer: They are determined from the isotopes of the elements.
Q4.
Will the isotopes of hydrogen H-1, H-2 and H-3 have the same chemical properties? Select the correct answer to explain why or why not.
Yes, as they have the same number of protons and a different number of neutrons
No, as they have a different number of neutrons
Correct answer: Yes, as they have the same number of electrons
Yes, as they have different number of neutrons
No, as they have the same number of protons and electrons
Q5.
Match the isotopes to the number of neutrons. Use your periodic table to help.

4 neutrons

3 neutrons

10 neutrons

12 neutrons