Question

For an atom of a given element, the number of electrons is given by.
A.the number of protons + number of neutrons
B.the atomic number of the element
C.the number of protons – number of neutrons
D.the mass number of the element

Answer 1

For an atom of a given element, it contains equal number of electrons and protons and the number of electrons or the number of protons is equal to atomic number of the element which is represented by Z.

Complete step by step answer:
Neutral atoms of each element contain an equal number of protons and electrons and the number of electrons determines an element’s atomic number and is used to distinguish one element from another.
The relationship between atomic number and the number of electrons or number of protons can be stated as follows:
Atomic number = number of protons per atom = number of electrons per neutral atom
Each element has got an atomic number. The atomic number is equal to the charge on the nucleus. It therefore is also equal to the number of protons in the nucleus and also equal to numerically the number of electrons in the neutral atom. The atomic number is represented by the symbol ‘Z’.
Different elements have different atomic numbers, it is therefore that the atoms of different elements contain different numbers of protons and electrons.
For example, the atomic number of Oxygen (O) is 8; so, we can say that its atoms contain 8 protons and 8 electrons.

Therefore, the correct answer is option (B).

Note: The number of neutrons is variable which results in isotopes, which are different forms of the very same atom that vary only in the number of neutrons that they possess. The mass number of an element is equal to the total number of protons and the number of neutrons. The number of electrons can also be different in atoms of the same element, thus producing ions called the charged atoms. For example, iron (Fe) can exist in its neutral state, or in the +2 and +3 ionic states.