# How to find the number of protons, electrons and neutrons

Neutrons, electrons and protons are the three main particles that make up an atom. As you can guess, protons have a positive charge, electrons carry a negative charge, and neutrons are just neutral particles. The mass of electrons is very low. However, neutrons and protons have similar masses. To find the number of protons, electrons and neutrons in an atom, just look at the periodic table of the elements, also called the Mendeleev table.

## Steps

### Part 1 of 2: Calculate the number of protons, electrons and neutrons

#### Step 1. Obtain a periodic table of the elements

This table will help you find the number of protons, electrons and neutrons in an element. This is a table that presents the elements according to their atomic structure. A color code makes it possible to distinguish the different elements. Each element is identified by a symbol comprising one, two or three letters. The table also shows other information such as the atomic mass and atomic number of each element.

• You can find this chart either by searching the internet or in a chemistry book.
• In exam papers, you will normally be allowed to use a periodic table of the elements.

#### Step 2. Identify your element on the periodic table

In the table, the elements are grouped according to their atomic number. They are divided into three main groups: metals, non-metals, and metalloids (semi-metals). Other groups include the alkali metals, halogens, and noble gases.

• It is easier to locate an element in the table by using its group (column) or its period (row).
• If you ignore the element's properties, you can search for its symbol.

#### Step 3. Locate the atomic number of the element

This number is marked in the upper left corner of the box, above the element symbol. The atomic number gives you the number of protons that make up the atom of the element in question.

### For example, the atomic number of boron (B) is equal to 5. So it has 5 protons

#### Step 4. Determine the number of electrons

The nucleus of an atom consists of protons which are positively charged particles. Electrons are negatively charged particles. Therefore, the number of protons and electrons of an element in the neutral state will be the same.

• For example, boron (B) has an atomic number of 5, so it has 5 protons and 5 electrons.
• However, if it is a positive or negative ion, the number of protons and the number of electrons will be different. You will need to calculate them. The charge of the ion is indicated in small print by an exponent after the corresponding element.

#### Step 5. Find the atomic mass of the element

This step will allow you to find the number of neutrons. You will first need to determine the atomic mass or atomic weight of the element. This data represents the average mass of the atoms of this element. It is listed under the element symbol.

### Be sure to round the atomic mass of the element to the nearest whole number. So, boron has an atomic mass of 10.811, but you will need to round it off to 11

#### Step 6. Differentiate between atomic number and atomic mass

To calculate the number of neutrons, you need to differentiate between the atomic number and the atomic mass. Remember you already know the atomic number. It is simply identical to that of protons.

### Part 2 of 2: calculate the number of electrons in an ion

#### Step 1. Find the electric charge of an ion

This number appears as a superscript after the element symbol. An ion is an atom that has a positive or negative charge due to the addition or removal of electrons. The number of protons in an atom does not vary. However, in an ion, the number of electrons is altered.

• Since an electron has a negative charge, it becomes positive after the removal of one or more electrons. On the other hand, the addition of electrons will have the effect of making the charge negative.
• For example, the charge of N3- is -3. On the other hand, that of Ca2+ is +2.
• Remember that this calculation is not necessary, if the element symbol is not followed by an exponent.

#### Step 2. Remove the charge from the atomic number

Originally, an ion with a positive charge is an atom that has lost electrons. To find the number of electrons, you need to subtract the extra charges from the atomic number. If the ion is positive, the number of protons is greater than that of electrons.

• For example, the charge of Ca2+ is equal to +2. As a result, it lost 2 electrons from its initial state. The atomic number of calcium is 20, so the ion has 18 electrons.

#### Step 3. Add a charge to the atomic number of negative ions

When an ion is negatively charged, the atom has more electrons. To calculate the total number of electrons, just add the number of additional charges to the atomic number. If the ion is negative, it has fewer protons than electrons.

• For example, the charge of N3- is -3. So, it carries 3 more electrons compared to its initial state. The atomic number of nitrogen is equal to 7. Therefore, this ion has 10 electrons.