4.1.4 Isotopes

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Key Points:

All atoms of the same element have the same number of protons.
Neutral atoms have the same number of electrons and protons.
Isotopes are atoms of the same element but with different masses, having the same number of protons but different numbers of neutrons.

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Example: Carbon-12, Carbon-13, and Carbon-14.

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Notation:

Isotopes and Nuclear Radiation

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Definition: Isotopes are different forms of the same element. They have the same number of protons but a different number of neutrons.

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Example: Oxygen:

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General Information:

All elements have different isotopes, but there are usually only one or two stable ones.

Ionising Radiation:
- Radioactive substances release ionising radiation from their nucleus.
- They can also release neutrons when they decay to rebalance the number of protons and neutrons.
Ionising Power:
- How easily a source of radiation loses electrons to create positive ions.

Unstable Nucleus:
- Some isotopes have an unstable nucleus.
- To become stable, the nucleus gives out radiation.
- This process is called radioactive decay.
- It is a totally random process.
Activity:
- The rate at which a source of unstable nuclei decay.
- Measured in becquerel (Bq).
- $1 \text{Bq} = 1 \text{decay per second}$
Measurement:
- A Geiger-Muller tube is used to measure the activity of a radioactive source.
- It is a detector.
Count-rate:
- The number of decays recorded each second.
- It is not the same as activity.