1. It becomes positively charged: Electrons carry a negative charge. When an electron is lost, the atom has more protons (positive charge) than electrons (negative charge), resulting in a net positive charge. This positively charged atom is called a cation.

2. It becomes an ion: Any atom that gains or loses electrons is called an ion. Since the atom in this case lost an electron, it's a positive ion or a cation.

3. Its electron configuration changes: The lost electron was in a specific energy level or orbital. This loss changes the atom's electronic structure, making it more stable in its new configuration.

4. Its chemical reactivity changes: The loss of an electron can significantly alter an atom's reactivity. Cations tend to be more reactive than their neutral atom counterparts, as they are looking to gain back an electron to regain stability.

5. It can form ionic bonds: Cations are highly attracted to anions (negatively charged ions). This attraction leads to the formation of ionic bonds, which are the electrostatic forces holding oppositely charged ions together.

Example:

Consider a neutral sodium atom (Na). It has 11 protons and 11 electrons. When it loses one electron, it becomes a sodium ion (Na+). The sodium ion now has 11 protons and 10 electrons, resulting in a net positive charge. It has a different electronic configuration and is more reactive than the neutral sodium atom.

Note: The process of losing an electron is called ionization. It can occur due to various factors like high temperatures, collisions with other particles, or interactions with electromagnetic radiation.