Question

What does the negative electronic energy (negative sign for all values of energy) for hydrogen atoms mean?
A ) the energy of an electron in the atom is lower than the energy of a free electron at rest which is taken zero.
B ) When the electron is free from the influence of the nucleus it has a negative value which becomes more negative.
C ) When the electron is attracted by the nucleus the energy is absorbed which means a negative value.
D ) Energy is released by the hydrogen atom in ground state.

Answer 1

Hint: An electron is far away from the nucleus, its energy is zero. When an electron approaches the nucleus, the electrostatic forces of attraction come into action. These forces increase the energy of the electron.

Complete answer:
> For hydrogen atoms, the sign of electronic energy is negative. This is because when an electron is in an atom, it has lower energy than if it is a free electron at rest. The free electron or electron at rest is the electron that is very very far away from the nucleus. The distance between the electron at rest and the nucleus is so large that no force is present between such an electron and nucleus. The energy of the free electron (or the electron at rest) is assigned a value zero.
> When the distance between the nucleus and the electron decreases, the magnitude of the energy increases due to forces present between electron and nucleus. But the sign of energy becomes negative. The ground state is the most stable state of the hydrogen atom. It is the state when the electron is present in the first energy level, with principal quantum number being equal to 1. When the electron is in the ground state, the energy of the electron is most negative.

Hence, the correct option is the option A ) the energy of an electron in the atom is lower than the energy of a free electron at rest which is taken zero.

Note: When an electron comes very close to the nucleus, the electrostatic forces of attraction are replaced with electrostatic forces of repulsion and the electronic energy becomes large positive.