Edexcel Combined Science CC3 – Atomic structure

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Atoms are small particles from which all substances are made. They are the smallest neutral part of an element that can take part in chemical reactions.
Tiny particle with a negative charge that is found in shells around the nucleus of an atom.
electron shell
Area around a nucleus that can be occupied by electrons, usually drawn as a circle (in ‘target diagrams’). Also called an electron energy level or an ‘orbit’.
A simple substance made up of only one type of atom.
Electrically neutral subatomic particle found in the nucleus of most atoms.
The positively charged centre of an atom.
A positively charge subatomic particle in the nucleus of all atoms.
relative charge
The electric charge of a subatomic particle compared to the charge on a proton.
relative mass
The mass of a subatomic particle compared to the mass of a proton.
subatomic particles
The smaller particles that make up atoms – protons, neutrons and electrons.
atomic number
The number of protons in the nucleus of an atom (symbol Z). Also known as the proton number.
mass number
The total number of protons and neutrons in the nucleus of an atom (symbol A). Also known as the nucleon number.
periodic table
Chart in which the elements are arranged in order of increasing atomic number.
Symbol for relative atomic mass (RAM).
Atoms of an element with the same number of protons (atomic number) but different mass numbers due to different numbers of neutrons.
An average calculated by adding up the values of a set of measurements and dividing by the number of measurements in the set.
nuclear fission
The reaction in which the nucleus of a large atom, such as uranium, splits into two smaller nuclei.
relative atomic mass (RAM)
The mean mass of an atom relative to the mass of an atom of carbon-12, which is assigned a mass of 12. The RAM of an element is the mean relative mass of the isotopes in the element.
Categories: Atomic Physics