Question

A neutral atom possesses 84 protons and 125 neutrons. What will be its mass number?​

Answer 1

Answer:209

Explanation:The mass number of an atom is equal to the sum of the no. of protons and neutrons.

Therefore,

No. of protons = 84.

No. of neutrons = 125

Mass No. = 84 + 125 = 209

Hope this helps.

Answer 2

Given:

A neutral atom possesses 84 protons and 125 neutrons.

To find:

Mass number of the atom ?

Calculation:

Mass number is often defined as the mass of the whole nucleus of the atom.

Now, we know that the nucleus of an atom contains protons and neutrons, so the mass number will be constituted by the sum of number of protons and neutrons.

Mass number is denoted as Z ;

$\rm \therefore \: Z = neutrons + protons$

$\rm \implies \: Z = 84 + 125$

$\rm \implies \: Z = 209$

So, mass number is 209.

Atomic number is equal to the number of electrons or protons. Hence , in this case, atomic number will be 84.

So, the atom will be represented as :

$\boxed{ \huge{X_{ \small{84}}^{ \small{209}} }}$