Question

As an atom becomes an ion, its mass number(1) decreases(2) increases(3) remains the same

Answer 1

As an atom becomes an ion, its mass number $\boxed{\left( 3 \right){\text{ remains the same}}}$  

Further explanation:

The smallest unit of an element is called an atom. It is also known as the building block of matter. An atom is generally represented as $_{\text{Z}}^{\text{A}}{\text{X}}$, where X is the symbol of the element, A is its atomic mass or mass number and Z is its atomic number.

The number of protons present in the atomic nucleus is termed as the atomic number (Z) whereas the total number of nucleons present in the nucleus of an atom is called mass number or atomic mass (A).

When electrons are either gained or lost from the neutral atom, it results in the formation of ions. Cations are the positively charged ions that are formed due to the removal of electrons from the neutral atom. Anions are the negatively charged ions that result from the addition of electrons to the neutral atom.

Since the formation of either type of ion requires gain or loss of electrons but mass number is the total number of protons and neutrons present in the atomic nucleus, the mass number remains the same when ions are formed from their respective ions. Therefore option (3) is the correct answer.

Consider an example of a sodium atom whose atomic number is 11 so it has an electronic configuration of $1{s^2}2{s^2}2{p^6}3{s^1}$. It loses one electron to form its monovalent ion, ${\text{N}}{{\text{a}}^ + }$ which has the configuration of $1{s^2}2{s^2}2{p^6}$. The number of electrons in Na is 11 while that in ${\text{N}}{{\text{a}}^ + }$ is 10. But both the species have same number of protons and neutrons in them. So the mass number remains unchanged if an atom forms its ions.

Learn more:

1. Component of John Dalton’s atomic theory: brainly.com/question/2357175

2. Basis of investigation for the scientists: brainly.com/question/158048

Answer details:

Grade: Senior School

Subject: Chemistry

Chapter: Atomic structure

Keywords: atom, matter, atomic nucleus, proton, electron, neutron, cations, anions, Na, 11, Na+, electronic configuration.

Answer 2

Becoming an ion involves gaining or losing electrons
Electrons have a relative mass of 0
So adding or removing them doesn't change the mass of the atom
So the answer is (3) remains the same