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:
8 protons in the nucleus.
Explanation:
The atomic number of an element is defined as the number of protons in the nucleus of an atom. In the case of oxygen, its atomic number is 8, meaning that an oxygen atom contains 8 protons in its nucleus. The atomic number is a fundamental property of an element because it determines the identity of the element and its position on the periodic table. The number of protons also directly influences the number of electrons in a neutral atom because, in a neutral atom, the number of electrons is equal to the number of protons to balance the overall charge.
Now, let’s clarify the other options:
- Electrons in 8 shells:
This statement is incorrect. The number of shells in an atom corresponds to the energy levels around the nucleus, but oxygen has only 2 electron shells. The first shell can hold up to 2 electrons, and the second shell can hold up to 8 electrons. Oxygen has 8 electrons in total, but only two shells. - A second shell with 8 electrons:
This is also incorrect. Oxygen has 8 electrons in total, but they are arranged in two electron shells. The first shell contains 2 electrons, and the second shell contains 6 electrons, not 8. The second shell can hold a maximum of 8 electrons, but in the case of oxygen, it has only 6 electrons in the second shell. - An atomic mass of 8:
This is incorrect because atomic mass refers to the total number of protons and neutrons in the nucleus of an atom. Oxygen’s most common isotope has an atomic mass of approximately 16, not 8. The atomic number is not the same as the atomic mass.
In summary, oxygen’s atomic number is 8 because it contains 8 protons in its nucleus, which defines its chemical identity as oxygen. This atomic number also determines its electron configuration, with 8 electrons in two shells, and dictates how oxygen interacts with other elements.