Final answer:
An overall charge in an atom is obtained when the atom gains or loses electrons, thus becoming an ion. A cation is formed when an atom loses electrons and has a positive charge; an anion is formed when an atom gains electrons and has a negative charge. The atomic charge is calculated as the number of protons minus the number of electrons.
Step-by-step explanation:
To understand how to get an overall charge in an atom, we need to consider the number of protons and electrons present in an atom. Atoms are typically electrically neutral, which means they have an equal number of protons and electrons. However, atoms can become ions by gaining or losing electrons. When an atom gains electrons, it becomes negatively charged and is known as an anion. Conversely, when it loses electrons, it becomes positively charged and is called a cation.
For instance, a neutral sodium atom has 11 protons and 11 electrons. If it loses one electron, it has more protons than electrons and thus has a net positive charge, making it a sodium cation with a +1 charge. On the other hand, a neutral oxygen atom has 8 protons and 8 electrons. If it gains two electrons, it becomes an oxygen anion with a -2 charge.
The atomic charge can be calculated using the formula:
Atomic charge = number of protons - number of electrons
This change in the number of electrons compared to protons determines the overall charge of the atom or ion.