Question

Oxygen is denoted as 16O *. How many protons and neutrons does an oxygen atom have?

Answer 1

Take a look at this picture here:
http://www.featurepics.com/FI/Thumb300/20100821/Chemical-Element-1639646.jpg

That's Oxygen,
in the way that it's shown on the periodic table of elements.

You see the number, at the top? 8

8 is the ATOMIC NUMBER.

The ATOMIC NUMBER is the number of ELECTRONS that oxygen has.
The ATOMIC NUMBER is also the number of PROTONS that oxygen has.

Now, look at the number on the bottom. 15.9

Round that number up to 16.

16 is the ATOMIC MASS.

The ATOMIC MASS is the SUM of all the PROTONS + the NEUTRONS.

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So, from this, we know that Oxygen has 8 Protons. (ATOMIC NUMBER 8)

We also know that Oxygen has 8 Electrons. (ATOMIC NUMBER 8)

But how many Neutrons does it have?

Look at the ATOMIC MASS.


Again,
ATOMIC MASS = PROTONS + NEUTRONS.

16 = 8 + NEUTRONS.

So, NEUTRONS = 8.