Yes, an electron can be lost from an atom, resulting in a positively charged atom. This process is known as ionization. Ionization can occur through various mechanisms, such as:
Electron impact ionization: High-energy electrons collide with an atom, transferring enough energy to remove one of its electrons. The atom then becomes a positively charged ion.
Photoionization: An atom absorbs a photon with sufficient energy to remove one of its electrons. This often occurs with high-energy ultraviolet (UV) or X-ray photons.
Thermal ionization: At high temperatures, atoms can gain sufficient thermal energy to overcome the attractive forces of the nucleus and lose an electron.
Electron capture: In some cases, an atom can capture an electron from its surroundings, resulting in the loss of an outer electron and the formation of a positively charged ion.
It's important to note that when an electron is lost from an atom, the resulting positively charged atom is called an ion. The number of protons in the nucleus remains the same, defining the atomic number of the element. However, the loss of an electron changes the atom's overall charge, making it positively charged.