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GCSE Physics · key term
The number of protons in a nucleus; it determines the element and its nuclear charge.
Used by OCR
Specification P6.1e · Paper 2 (Foundation), Paper 4 (Higher)
Revise: Emission effectsWhen a nucleus emits one, it loses four nucleons altogether: its mass number falls by 4 and its proton number falls by 2. Its positive charge therefore decreases, and the remaining nucleus is a different element. For instance, after uranium-238 emits an alpha particle, the remaining nucleus has mass number 234 and proton number 90, making it thorium-234.
Paper 1, Paper 2
The number of protons in a nucleus, represented by ; it determines the element.
Revise: Isotopes and Radioactive EmissionsIsotopes are nuclei of the same element with the same proton number but different neutron numbers. They consequently have different mass numbers.
State changes to both mass number and proton number when describing an emission.
For beta emission, the proton number increases by one: a neutron becomes a proton while the electron leaves the nucleus.
Identify the daughter element from its new proton number, not from its mass number.
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