Question

Which of the following statements is correct?
1.The mass number is equal to the number of protons and electrons.
2.The number of electrons is equal to the number of neutrons in an atom.
3.The atomic number is equal to the mass number of an atom.
4.The atomic number is the number of electrons in a neutral atom.

Answer 1

Hint: We have to know that the electrons contribute greatly to the atom’s charge, as each electron has a negative charge equal to the positive charge of a proton. Scientists define these charges as +1 and -1. In an uncharged, neutral atom, the number of electrons orbiting the nucleus is equal to the number of protons inside the nucleus.

Complete answer:
We will look at all the statements one by one to answer this question.
Statement 1 is incorrect which says that mass number is equal to the number of protons and electrons is wrong as the number of protons and the number of neutrons determine an element’s mass number.
Statement 2 is incorrect as in a neutral atom the number of electrons and number of protons is equal and not the number of neutrons.
Statement 3 is incorrect as atomic number is not equal to mass number of an atom.
Statement 4 this statement is correct as atomic number is the number of protons or number of neutrons and in a neutral atom the number of protons and number of electrons are equal.

Statement 4 is the correct.

Note:
As we know that neutral atoms of an element contain an equal number of protons and electrons. We need to remember that the number of protons determines an element’s atomic number (Z) and distinguishes one element from another. For example, carbon’s atomic number (Z) is 6 because it has 6 protons. We have to know that the number of neutrons can vary to produce isotopes.