# I Atomic Number

### How do you calculate atomic number of an element?

The number of atoms or molecules (n) in a mass (m) of a pure material having atomic or molecular weight (M) is easily computed from the following equation using Avogadro's number (NA = 6.022×10 23 atoms or molecules per gram-mole): M mN n A (1) In some situations, the atomic number density (N), which is the concentration of atoms or molecules per. Here is a list of the elements sorted by atomic number.Element nameElement symbolAtomic numberHydrogenH1HeliumHe2LithiumLi3.

## 1 Answer

Number of protons, number of electrons, mass number minus number of neutrons.

#### Explanation:

Some questions are considered as trick questions but they are not.

## I Atomic Number And Mass

Example:

The element X has a mass number of 20 and it has 10 protons/electrons. What is the atomic number?

Answer:

1 Atomic number is the number of protons so the answer is 10.

2 It is also the number of electrons because, elements have no overall charge as the positive protons cancel out the negative electrons. In order for this cancellation to happen, the number of protons and electrons must the same. Therefore, if the question only gives the number of electrons, you write the number of electrons as the answer.

Example:

The element Y has a mass number of 30 and has 20 neutrons. What is the atomic number?

When you find the number of neutrons of an element, you do mass number minus atomic number. You can use this to build an equation:

30-x=20

x=10

The atomic number is 10