How many valence electrons does oxygen have? What is the charge on an oxygen ion?
(1 point)
a. 2,-2
b. 6, -2
c. 2, +2
d. 6, +2
The Correct Answer and Explanation is:
The correct answer is b. 6, -2.
Explanation:
- Valence Electrons of Oxygen:
Oxygen (O) is in Group 16 of the periodic table, also known as the chalcogens. The number of valence electrons in an element is determined by its group number. Group 16 elements have 6 valence electrons. This means oxygen has 6 electrons in its outermost shell, which can be used to form bonds with other elements. The electronic configuration of oxygen is 1s² 2s² 2p⁴, indicating that its outermost shell (the second shell) has 6 electrons. These 6 electrons are the valence electrons that oxygen can share, gain, or lose when forming chemical bonds. - Charge on an Oxygen Ion:
When oxygen forms an ion, it tends to gain electrons to achieve a stable electron configuration. Oxygen has 6 valence electrons and needs 2 more electrons to complete its outer shell and reach the stable electron configuration of the nearest noble gas, neon (Ne), which has 8 electrons in its outer shell. By gaining 2 electrons, oxygen forms an O²⁻ ion. This negative charge arises because the oxygen atom now has 8 electrons but only 6 protons, resulting in a net negative charge of -2. The gained electrons make the ion negatively charged, with a charge of -2. In summary, oxygen has 6 valence electrons and, when it forms an ion, it typically gains 2 electrons, resulting in a charge of -2. This is why the correct answer is b. 6, -2. Oxygen’s tendency to gain 2 electrons is essential for its chemistry, as it allows oxygen to readily form negative ions and participate in various chemical reactions, such as in the formation of water (H₂O) and other compounds.