Question

3. Answer in one word.
a. The number of electrons present in the outer shell of an atom
b. The number of electrons present in different shells of the atom
c. The fixed orbits in which an atom revolves without gain or loss of energy
d. The atoms which have the same atomic number but different mass numbers
e. The sum of protons and neutrons present in the nucleus of an atom​

Answer 1

Answer:

1. Eight electrons
2. Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2) electrons.
3. According to postulated of Bohr's atomic model, the electron has a definite amount of energy and electron does not lose or gain while moving in the orbit. Electrons revolve around the nucleus in concentric circular orbits at fixed distance from nucleus.  These are stationary orbits and the energy of electrons in these orbits is constant. As long as electrons revolve in these stationary orbits, they do not radiate energy.
4. Isotopes
5. Mass number