The atomic number is the number of protons in the nucleus. It indicates the amount of positive charge in the nucleus and is unique for every element. An atom is electrically neutral because the number of protons is equal to number of electronsThe mass number is the number of neutrons and protons in the nucleus. It gives an indication of the mass of the nucleus relative to the average mass of a neutron and proton.
Atomic Number and Mass Number
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Specification: Edexcel Chemistry (8CH0), AS-level, Topic 1: Atomic Structure and the Periodic Table. Topic: Atomic Structure.
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All 19 lessons in Atomic Structure · All Edexcel AS-level Chemistry topics