ANS:A - number

The term "atomic number" refers to a fundamental concept in chemistry and physics that represents the number of protons found in the nucleus of an atom. Here's an explanation of the term "number" in the context of atomic number:

1. Atomic Number: The atomic number of an element is denoted by the symbol �Z. It is a whole number that uniquely identifies each element in the periodic table. For example, hydrogen (H) has an atomic number of 1, helium (He) has an atomic number of 2, and so on. The atomic number determines the identity of an element because it is equal to the number of protons in the nucleus of its atoms.
2. Protons: Protons are subatomic particles with a positive electric charge. They are one of the three main constituents of an atom, along with neutrons and electrons. In a neutral atom, the number of protons is equal to the number of electrons, which balances the positive charge of the protons, resulting in a net neutral charge for the atom.
3. Element Identity: The atomic number uniquely identifies each element because it determines the number of protons in the nucleus. Since atoms of different elements have different numbers of protons, they also have different atomic numbers. For example, carbon (C) has six protons, nitrogen (N) has seven protons, and oxygen (O) has eight protons. Therefore, the atomic number is a key characteristic used to classify and organize elements in the periodic table.