A Level Physics Practice Exam

What is the lowest energy state of an atom known as?

1. Excited state

2. Ground state

3. Valence state

4. Stable state

The correct answer is: Ground state

The lowest energy state of an atom is referred to as the ground state. In this state, the electrons are organized in their lowest possible energy levels around the nucleus, meaning they are as close as possible to the nucleus without gaining more energy. When an atom absorbs energy, electrons can be excited to higher energy levels, which is referred to as the excited state. The ground state is important because it is the most stable configuration for the atom, and any energy absorption that leads to an excited state will eventually result in the atom returning to the ground state, releasing energy in the process—typically in the form of light or heat. The term valence state is not commonly used in this context; it usually refers to the state of an atom with regard to its ability to bond with other atoms, which doesn't directly correlate with energy levels. Similarly, the term stable state can be misleading, as atoms can have multiple stable configurations depending on circumstances and energy levels, but the ground state is specifically defined as the lowest energy level. Therefore, ground state effectively captures the essence of an atom's lowest energy configuration and distinguishes it from other states of excitation and bonding.