What is the atomic nucleus?
The atomic nucleus :
Theconstitutes the heart of the . Ernest Rutherford was the first to highlight it. Located in the center of the , it has a diameter of around 10 -15 meters, compared to 10 -10 meters for the atom as a whole.
Mass and structure of the atomic nucleus
The nucleus contains some 99.97% of theof an atom. The density of in an atomic nucleus is around 230,000 tonnes per cubic millimeter!
The nucleus of atoms is made up of:
and are also called . The atomic nucleus is therefore positively charged and its cohesion is essentially ensured by the .
Number of protons and number of neutrons
The number of protons in an atomic nucleus defines the. It is noted Z and called .
The number ofcan vary to give rise to of the element. Thus, the 12 and are two carbon isotopes. They both count 6 protons, but the first counts 6 neutrons while the second counts 8.
Stable nuclei, unstable nuclei
When the bindingof an atomic nucleus is large enough, the nucleus is said to be stable. When it is too low, it causes instability. An unstable atomic nucleus is called a .
It emits a radiation α (alpha) and β (), usually accompanied by an γ (gamma) emission of . The number of protons – and neutrons – then changes. There is from one element to another. For example, a atom 210, which has 84 protons and 126 neutrons, can become, by α , a atom 206 containing 82 protons and 124 neutrons.
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