What is Atomic number?
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.
What is Mass number
The helium atom has a mass number of 4 and atomic number of 2
Example:
What is the mass number and atomic number of the ?
Solution:
Mass number = 31, atomic number = 15
Number of neutrons = mass number – atomic number
Example:
How many neutrons are there in one atom of ?
Solution:
Mass number = 24
Atomic number = 12
Number of neutrons = mass number – atomic number = 24 – 12 = 12
Example:
How many neutrons are there in one atom of ?
Solution:
Mass number = 307
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.
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