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More Lessons for Chemistry

Math Worksheets

**What is Atomic number?**

**What is Mass number**

**Example;** **Number of neutrons = mass number – atomic number **

Atomic number = 12

Number of neutrons = mass number – atomic number = 24 – 12 = 12

Atomic number = 82

Number of neutrons = mass number – atomic number = 207 – 82 = 125

Atomic number, mass number, and isotopes

How to use the atomic number and the mass number to represent different isotopes
The following video shows an example of calculating the number of neutrons.

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

More Lessons for Chemistry

Math Worksheets

- The number of protons in the nucleus of an atom is called the
**atomic number**. - It is represented by the symbol
*Z*

*Example: *

Helium has an atomic number of 2 since it has two protons in its nucleus.

Lithium has an atomic number of 3 since it has three protons in its nucleus.

- The
**mass number**is the total number of neutrons and protons in the nucleus of the atom. - It is also called the
**nucleon number**. - It is represented by the symbol
*A* - The atomic number and the mass number of an element is usually written in the following way:

The helium atom has a mass number of 4 and atomic number of 2

What is the mass number and atomic number of the ?

*Solution: *

Mass number = 31, atomic number = 15

*Example: *

How many neutrons are there in one atom of ?

*Solution: *

Atomic number = 12

Number of neutrons = mass number – atomic number = 24 – 12 = 12

*Example: *

How many neutrons are there in one atom of ?

*Solution: *

Atomic number = 82

Number of neutrons = mass number – atomic number = 207 – 82 = 125

How to use the atomic number and the mass number to represent different isotopes

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You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.

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