Determine the number of protons neutrons and electrons in the following

The correct answer is option C.

From the given data it is inferred that the atomic number and mass number of element X are 29 and 65 respectively.

The number of protons (p+) and electrons (e-) of an atom will be equal to its atomic number. This suggests that the number of p+ and e- in the given case is 29.

The number of neutrons (n⁰) in the given case can be calculated by subtracting the atomic number from the mass number as follows-

n⁰ = 65-29 = 36

Hence it can be concluded that,

p+ = 29, n⁰ = 36, e- = 29

This suggests that option C is the correct choice.

Lessons

How to Find the Number of Protons, Neutrons, and Electrons. Step by Step Explanation with Examples

In this post, we’ll be going over how to determine the number of protons, neutrons, and electrons in an atom or ion.

We’ll first start by discussing what each of the components in the nuclide notation means. Then we’ll go through two examples together. 

The Nuclide Notation

 

The letter(s) in the middle is the symbol of the element.

The number on the bottom left corner is the atomic number, which tells you the number of protons.

The number on the upper left corner is the mass number, which is equal to the neutrons and protons added together.

Lastly, the charge is on the upper right corner. If there isn’t any number or signs, then it means that atom has no charge and is neutral. 

Rules to Finding Number of Protons, Neutrons, and Electrons

# of protons = atomic number

# of neutrons = mass number – atomic number

# of electrons = atomic number – charge

That’s it!

Examples

Great, lets apply the rules to some examples. 

# of protons = 17 

# of neutrons = 37 – 17 = 20

# of electrons  = 17 – 0 = 17

# of protons = 16 (the atomic number is not given, but can be found on the periodic table)

# of neutrons = 32 – 16 = 16

# of electrons = 16 – (-2) = 18

Additional Practice

Try these on your own and check the answer below 

  1. 78Se2-
  2. 39K+

ANSWERS

  1. 34 protons, 44 neutrons, 36 electron
  2. 19 protons, 20 neutrons, 18 electron

Additional Resources

More practice problems

Answers to practice problems

If you have any questions, leave a comment below. 

How many protons, electrons and neutrons are in an atom of krypton, carbon, oxygen, neon, silver, gold, etc...?

To find the number of protons, electrons and neutrons in an atom, just follow these easy steps:

Step 1 - Gather Information

The first thing you will need to do is find some information about your element. Go to the Periodic Table of Elements and click on your element. If it makes things easier, you can select your element from an alphabetical listing.

Use the Table of Elements to find your element's atomic number and atomic weight. The atomic number is the number located in the upper left corner and the atomic weight is the number located on the bottom, as in this example for krypton:

Step 2 - The Number of Protons is...

The atomic number is the number of protons in an atom of an element. In our example, krypton's atomic number is 36. This tells us that an atom of krypton has 36 protons in its nucleus.

The interesting thing here is that every atom of krypton contains 36 protons. If an atom doesn't have 36 protons, it can't be an atom of krypton. Adding or removing protons from the nucleus of an atom creates a different element. For example, removing one proton from an atom of krypton creates an atom of bromine.

Step 3 - The Number of Electrons is...

By definition, atoms have no overall electrical charge. That means that there must be a balance between the positively charged protons and the negatively charged electrons. Atoms must have equal numbers of protons and electrons. In our example, an atom of krypton must contain 36 electrons since it contains 36 protons.

Electrons are arranged around atoms in a special way. If you need to know how the electrons are arranged around an atom, take a look at the 'How do I read an electron configuration table?' page.

An atom can gain or lose electrons, becoming what is known as an ion. An ion is nothing more than an electrically charged atom. Adding or removing electrons from an atom does not change which element it is, just its net charge.

For example, removing an electron from an atom of krypton forms a krypton ion, which is usually written as Kr+. The plus sign means that this is a positively charged ion. It is positively charged because a negatively charged electron was removed from the atom. The 35 remaining electrons were outnumbered by the 36 positively charged protons, resulting in a charge of +1.

Step 4 - The Number of Neutrons is...

The atomic weight is basically a measurement of the total number of particles in an atom's nucleus. In reality, it isn't that clean cut. The atomic weight is actually a weighted average of all of the naturally occurring isotopes of an element relative to the mass of carbon-12. Didn't understand that? Doesn't matter. All you really need to find is something called the mass number. Unfortunately, the mass number isn't listed on the Table of Elements. Happily, to find the mass number, all you need to do is round the atomic weight to the nearest whole number. In our example, krypton's mass number is 84 since its atomic weight, 83.80, rounds up to 84.

The mass number is a count of the number of particles in an atom's nucleus. Remember that the nucleus is made up of protons and neutrons. So, if we want, we can write:

Mass Number = (Number of Protons) + (Number of Neutrons)

For krypton, this equation becomes:

84 = (Number of Protons) + (Number of Neutrons)

If we only knew how many protons krypton has, we could figure out how many neutrons it has. Wait a minute... We do know how many protons krypton has! We did that back in Step 2! The atomic number (36) is the number of protons in krypton. Putting this into the equation, we get:

84 = 36 + (Number of Neutrons)

What number added to 36 makes 84? Hopefully, you said 48. That is the number of neutrons in an atom of krypton.

The interesting thing here is that adding or removing neutrons from an atom does not create a different element. Rather, it creates a heavier or lighter version of that element. These different versions are called isotopes and most elements are actually a mixture of different isotopes.

If you could grab atoms of krypton and count the number of neutrons each one had, you would find that most would have 48, others would have 47, some would have 50, some others would have 46, a few would have 44 and a very few would have 42. You would count different numbers of neutrons because krypton is a mixture of six isotopes.

In Summary...

For any element:

Number of Protons = Atomic Number

Number of Electrons = Number of Protons = Atomic Number

Number of Neutrons = Mass Number - Atomic Number

For krypton:

Number of Protons = Atomic Number = 36

Number of Electrons = Number of Protons = Atomic Number = 36

Number of Neutrons = Mass Number - Atomic Number = 84 - 36 = 48

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