Which of the following is true about an electron? (A) It is located closer to the nucleus when excited. (B) It is located in the nucleus when excited. (C) It is located farther from the nucleus when excited. (D) It is located farther from the nucleus when in its ground state.
Electrons that are in the ground state have the lowest energy. For example, hydrogen’s single electron is in the ground state when it’s in the first energy level, as the first energy level has the lowest energy. When an electron is excited, it occupies a higher energy level. In the hydrogen atom, the electron is excited when it occupies any energy level higher than the first energy level. As we can see from this diagram, the lower energy levels are closer to the nucleus than the energy levels with a higher energy. So electrons are located farther from the nucleus when excited.
However, we should know that these diagrams, which represent the Bohr model of the atom, are not entirely accurate descriptions of the electrons in an atom. According to modern atomic theory, electrons have properties that are both particle-like and wavelike. Since the Bohr model describes the electron as a particle orbiting the nucleus, it doesn’t capture the wavelike properties of the electron. To describe the wavelike properties of the electron, modern atomic theory describes the electron as more of a cloud that’s spread out in space around the nucleus of the atom. The shape of this cloud is described by a mathematical function that is called an atomic orbital.
Atomic orbitals increase in size as the energy level increases. This means electrons in the first energy level have a higher probability of being closer to the atomic nucleus than electrons that are in higher energy atomic orbitals. So this is still in line with what we discussed using the Bohr model of the atom. When the electron is in the ground state, it occupies a lower energy level, which is closer to the nucleus. When the electron is excited, it has a higher energy. So it’s located further from the nucleus.
Of the answer choices, the one that was true about an electron was answer choice (C). It is located farther from the nucleus when excited.