An atom's identity is determined primarily by the number of protons in its nucleus, which is known as the atomic number. Each element on the periodic table is defined by a unique atomic number. For example, hydrogen has one proton (atomic number 1), while carbon has six protons (atomic number 6).
In summary:
- Atomic number: The number of protons in the nucleus defines the element.
- Element type: The specific arrangement and number of protons classify the atom as a specific element, such as oxygen, nitrogen, or gold.
While the number of neutrons (which contributes to the atomic mass) and electrons (which affect the atom's ionization state and chemical behavior) can vary, they do not change the identity of the atom itself. Variants of an element with the same number of protons but different numbers of neutrons are called isotopes.
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