A - 20, B-40, C -Ca, D-10, E-9 and F-F.
What is an atom?
An atom consists of a central nucleus that is usually surrounded by one or more electrons.
The number of protons of A is =20
The number of protons of D is =10
The number of neutrons of E is =9
The atomic number of B is =40
The element symbol of C is = Ca
The element symbol of F is = F
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