# How many protons and neutrons are in an atom of Mo-94?

Jul 6, 2016

$94$ protons and neutrons.

#### Explanation:

This is a great example of a question that actually provides you with the answer.

The quick answer here is that there are $94$ protons and neutrons in a molybdenum-94 isotope, $\text{^94"Mo}$.

That is the case because an element's isotopes are distinguished using their mass number, which is added to the name of the isotope using a hypen.

As you know, the mass number, $A$, tells you the number of nucleons present in the nucleus. A nucleon is simply a proton or a neutron.

This means that the mass number of a given isotope essentially tells you how many protons and neutrons are present in its nucleus.

In your case, molybdenum-94 has a mass number of $94$, which means that it contains $94$ protons and neutrons in its nucleus.

To find the specific number of protons and of neutrons, grab a periodic table and look for molybdenum, $\text{Mo}$. You'll find the element listed in period 5, group 6.

Its atomic number, $Z$, which tells you how many protons are present in the nucleus, is equal to $42$. This means that the nucleus of any isotope of molybdenum will contain $42$ protons.

This leaves you with

$\text{no. of neutrons} = A - Z$

$\text{no. of neutrons" = 94 - 42 = "52 neutrons}$