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 determined by the number of protons in its nucleus. For oxygen, this number is 8, meaning it has 8 protons in its nucleus. The atomic number is the fundamental identifier for each element on the periodic table. It is the key property that distinguishes one element from another.
The relationship between protons, electrons, and the atomic number:
- Protons and Atomic Number:
The atomic number directly corresponds to the number of protons in the nucleus of an atom. Oxygen, with an atomic number of 8, has exactly 8 protons. This is a defining characteristic of oxygen. No other element has 8 protons; hence, oxygen is uniquely identified by its atomic number 8. - Electrons:
In a neutral oxygen atom, the number of protons is equal to the number of electrons. Therefore, oxygen also has 8 electrons. These electrons are arranged in energy levels or shells around the nucleus. Oxygen has two electron shells: the first shell contains 2 electrons, and the second shell contains 6 electrons. The electrons in the outermost shell (valence electrons) are important in determining the chemical reactivity of oxygen. - Shells:
Oxygen does not have 8 electron shells; it only has 2. The concept of 8 electrons in an outer shell does apply to elements with higher atomic numbers like neon (which has a full outer shell of 8 electrons), but oxygen itself only has 6 electrons in its second shell. - Atomic Mass:
The atomic mass of oxygen is approximately 16, not 8. The atomic mass is the sum of protons and neutrons in the nucleus. Since oxygen typically has 8 neutrons in addition to its 8 protons, the mass is about 16 atomic mass units (AMU), which is unrelated to the atomic number.
In conclusion, the atomic number of oxygen is 8 because it has 8 protons in its nucleus, which defines the element oxygen in the periodic table.