In a solid at room temperature, most of the atoms are not in their ground state. The ground state of an atom refers to the lowest energy level that an electron can occupy in an atom. According to the principles of quantum mechanics, electrons in an atom can occupy different energy levels or orbitals.
At room temperature, the atoms in a solid have gained thermal energy from their surroundings. This thermal energy causes the atoms to vibrate and the electrons to move between different energy levels. As a result, the electrons in the atoms can occupy excited states, which are higher in energy than the ground state.
The distribution of electrons among different energy levels follows the principles of statistical mechanics. According to the Boltzmann distribution, at higher temperatures, there is an increasing probability that electrons will occupy higher energy levels. Therefore, at room temperature, many atoms in a solid will have electrons in excited states rather than the ground state.
It is important to note that some atoms in a solid may still be in their ground state at room temperature, especially in materials with large energy gaps between the ground state and excited states. Additionally, there may be localized regions or defects where certain atoms are in their ground state. However, on average, a significant portion of the atoms in a solid at room temperature will have electrons in excited states.