When an atom loses or gains an electron, it undergoes a process called ionization, resulting in the formation of an ion. The specific changes that occur depend on whether the atom loses an electron (forming a positive ion) or gains an electron (forming a negative ion). Let's look at both scenarios:
- Losing an electron (formation of a positive ion): When an atom loses one or more electrons, it becomes positively charged. The loss of negatively charged electrons creates an imbalance between the positive protons in the nucleus and the remaining negative charges. The atom that has lost an electron is now called a cation.
For example, let's consider sodium (Na) losing one electron. A neutral sodium atom (Na) has 11 protons and 11 electrons. When it loses one electron, it becomes a sodium ion (Na+), which has 11 protons and 10 electrons. The positive charge of the sodium ion indicates that it has one more proton than electrons.
- Gaining an electron (formation of a negative ion): When an atom gains one or more electrons, it becomes negatively charged. The addition of negatively charged electrons offsets the positive charge of the protons, leading to an excess of negative charges. The atom that has gained an electron is now called an anion.
For example, let's consider chlorine (Cl) gaining one electron. A neutral chlorine atom (Cl) has 17 protons and 17 electrons. When it gains one electron, it becomes a chloride ion (Cl-), which now has 17 protons and 18 electrons. The negative charge of the chloride ion indicates that it has one more electron than protons.
The formation of ions, whether positive or negative, is essential in various chemical reactions and the formation of ionic compounds. Ions interact with other ions or molecules, and their charges influence their behavior and chemical properties.