​Let's Learn Something New!

​WHAT IS THE ATOMIC MASS OF AN ATOM?

​Each ELEMENT has an ATOMIC WEIGHT that is equal to the number of protons plus the number of neutrons (in one atom of the element).

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​Oxygen has an atomic number of 8 and atomic mass of 15.999. We can determine the number of NEUTRONS in an oxygen atom.

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​That's right! We can find the # of neutrons in an oxygen atom because we already know the number of protons.

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​The number of protons in an atom is equal to the atomic number of the atom.

An atom of oxygen has 8 protons.

​To find the number of neutrons in an oxygen atom:

1. Round the atomic mass to the nearest whole number.                  2. Subtract the atomic number from the rounded atomic mass.

​1. 15.999 rounds to 16.

2. Atomic mass - atomic number = # of neutrons.

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Answer: 16-8= 8 neutrons

​Find the number of neutrons in an atom of boron.

1. Round the atomic mass to the nearest whole number.

​2.  Subtract the atomic number from 11.

What is your answer?

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6 is the number of neutrons in a boron atom.

Great job!​

​How many neutrons are in an atom of lithium?

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​1. Round the atomic mass to the nearest whole number.

​2. Subtract the atomic number from the atomic mass.