The atomic number of oxygen is 8 because oxygen has?
8 protons in the nucleus.
electrons in 8 shells.
a second shell with 8 electrons.
an atomic mass of 8.
The correct answer and explanation is :
The correct answer is:
Oxygen has 8 protons in the nucleus.
Explanation:
The atomic number of an element is defined as the number of protons in its nucleus. This number is unique to each element and determines the element’s identity. For oxygen, the atomic number is 8, which means it has 8 protons in its nucleus.
In addition to protons, oxygen also has electrons orbiting its nucleus. In a neutral atom, the number of electrons equals the number of protons. So, oxygen has 8 electrons. These electrons are arranged in shells or energy levels around the nucleus, but the number of electrons doesn’t directly determine the atomic number.
Now, let’s address the other options:
- Electrons in 8 shells: This is incorrect. Electrons are arranged in shells around the nucleus, but oxygen only has 2 electron shells. The first shell holds 2 electrons, and the second shell holds 6 electrons, adding up to the 8 electrons total. There are not 8 shells in oxygen’s electron configuration.
- A second shell with 8 electrons: This is also incorrect. The second shell in oxygen’s electron configuration has only 6 electrons. The first shell holds 2 electrons, while the second shell holds 6, not 8.
- An atomic mass of 8: This is incorrect as well. The atomic mass of oxygen is approximately 16 atomic mass units (amu), not 8. The atomic mass is approximately the sum of protons and neutrons in the nucleus. While oxygen has 8 protons, it usually has 8 neutrons, giving it an atomic mass of about 16.
Therefore, the atomic number of oxygen is 8 because it has 8 protons in its nucleus, making it oxygen and giving it its chemical properties.