No Of Electrons


Electrons always exist in the circuit as part of the atoms and molecules that make up the circuit. The electrical energy that is delivered is the result of the electrons moving through the circuit. Turn off the pump (i.e. Disconnect the battery), and the electrons stop moving through the circuit. But the electrons don't go away. Thus, 12-2= 10 electrons. Symbol of an ion. Likewise, to calculate the number of electrons for an ion that carries a negative charge, you must recall that when an ion carries a negative charge, the number of electrons are more than the number of protons. So to get the number of electrons, you must add the size of charge to the atomic or proton.

How many electrons are in #n=3#, #l= 2#?

1 Answer


The idea here is that you must use the value of the angular momentum quantum number, #l#, which tells you the energy subshell in which an electron resides, to find the possible values of the magnetic quantum number, #m_l#.

The number of values that the magnetic quantum number can take tells you the number of orbitals that are present in a given subshell.

So, you know that the magnetic quantum number depends on the value of the angular momentum quantum number

#m_l = {-l, -(l-1), .., -1, color(white)(-)0, +1, .., +(l-1), +l}#

In your case, you have #l=2#, which is an accepted value for the angular momentum quantum number given the fact that the principal quantum number, #n#, is equal to #3#, so you can say that

#m_l = {-2, -1, color(white)(-)0, +1, +2}#

This tells you that the #d#subshell, which is denoted by #l=2#, holds a total of #5#orbitals.

Since each orbital can hold a maximum of #2#electrons, one having spin-up and one having spin-down, you can say that you have

#5 color(red)(cancel(color(black)('orbitals'))) * '2 e'^(-)/(1color(red)(cancel(color(black)('orbital')))) = '10 e'^(-)#

Therefore, a maximum number of #10#electrons can share these two quantum numbers in an atom.

#n=3, l=2#

These electrons are located on the third energy level, in the#3d#subshell.

Related questions

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)

How Many Valence Electrons No

No Of Electrons

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..

No Of Electrons In M Shell

For any element:

Number of Protons = Atomic Number

No Of Electrons

Number of Electrons = Number of Protons = Atomic Number

Hydrogen With No Electrons

Number of Neutrons = Mass Number - Atomic Number

For krypton:

Number of Protons = Atomic Number = 36

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

Not getting messages on iphone 7. Number of Neutrons = Mass Number - Atomic Number = 84 - 36 = 48

No Of Electrons In Potassium

Related Pages:

No Of Electrons In Carbon

For questions about this page, please contact Steve Gagnon.