Question

Suppose an oxygen atom gains two electrons to become an oxygen ion. What is its electric charge?

Short answer

The oxygen ion has a charge of -2.

Step-by-step solution

Understand the Oxygen Atom

An oxygen atom typically has 8 protons, which are positively charged, and 8 electrons, which are negatively charged. This makes it electrically neutral because the number of protons equals the number of electrons.

Determine the Gain of Electrons

When the oxygen atom gains two electrons, it now has 10 electrons. Electrons have a negative charge, so gaining electrons makes the atom negatively charged.

Calculate the Overall Charge

Initially, the oxygen atom is neutral because it has an equal number of protons and electrons. Each electron has a charge of -1. Therefore, gaining two electrons results in a charge of 2 x -1 = -2.

Key concepts

Atomic Structure

Every atom is made up of three main types of particles: protons, neutrons, and electrons. These particles are arranged in a structure centered around the nucleus. The nucleus contains protons, which have a positive charge, and neutrons, which have no charge at all.
Outside the nucleus, electrons orbit in various energy levels or shells. Electrons have a negative charge that balances out the positive charge of protons.
- **Protons** are positive - **Neutrons** are neutral - **Electrons** are negative Oxygen atoms, like all atoms, are usually electrically neutral. This neutrality is due to having an equal number of protons and electrons; in this case, 8 of each. This means the overall charge of the oxygen atom is zero when it is in its standard atomic state.

Electron Gain

When an oxygen atom gains electrons, it transforms into an oxygen ion. Electrons are negatively charged, so adding them increases the overall negative charge of the atom.
It's important to note that gaining electrons is a common process when atoms seek to achieve a stable electronic configuration. Oxygen aims to fill its outer shell by gaining electrons because its valence shell initially holds 6 electrons and needs to reach 8 to be complete (following the octet rule).
By gaining two electrons, oxygen achieves a stable electronic configuration similar to the noble gases. This gain of electrons leads to the formation of an oxide ion, which is essential for various chemical reactions and compounds, including water and many minerals. In this ionized state, oxygen is no longer neutral and has a surplus of electrons that affects its interaction with other elements.

Electric Charge Calculation

Electric charge calculations help determine the charge of an ion after electron gain or loss. Since each electron carries a charge of \(-1\), gaining extra electrons results in a negative charge.
Initially, the oxygen atom has no net charge because the number of protons and electrons is the same. When oxygen gains two electrons:

• Initial state: 8 protons (\(+8\)) and 8 electrons (\(-8\)) equals a total charge of 0.
• Upon gaining 2 electrons: 8 protons (\(+8\)) and 10 electrons (\(-10\)).
• Calculate new charge: \(8 - 10 = -2\).

The result is an ion with a net charge of \(-2\). This negative charge is indicative of an increase in electrons compared to protons, confirming that the oxygen ion is now negatively charged.