Question

What is nucleus of an atom? Compare its size with that of the atom. Name its constitutents. How is the number of these constituents determined by the atomic number its atomic model.

Answer 1

The nucleus at the centre of atom, whose size is of the order of 10^-15 m to 10^-14 m.

The size of a nucleus is 10^-5 to 10^-4 times the size of an atom. It consists of protons and neutrons.

If Z is the atomic number and A is the mass number of an atom, then the atom contains Z number of electrons; Z number of protons and A - Z number of neutrons.

The atom is specified by the symbol $${\phantom{A}}_{\phantom{\mathrm{Z}}}^{\phantom{\mathrm{A}}}{\phantom{A}}_{\phantom{2}\mathrm{Z}}^{\phantom{2}\mathrm{A}}\mathrm{X}$$ where X is the chemical symbol for the element.