Video Transcript
A nitrogen atom has the chemical
symbol nitrogen-14. How many protons does the nitrogen
atom have? How many neutrons does the nitrogen
atom have?
To figure out the answer to these
questions, let’s take a closer look at this chemical symbol. In this symbol, the capital 𝑁 is
the shorthand abbreviation for the element nitrogen. Then the number to the lower left
of that symbol, in this case seven, is called the atomic number. This number represents the number
of protons in the nucleus of the particular element we’re talking about, in this
case nitrogen.
If we represented the nucleus of
this nitrogen atom by this space, then the atomic number of seven means that there
are one, two, three, four, five, six, seven protons in this nucleus. And that gives us the answer to our
first question. The number of protons this nitrogen
atom has is seven.
Next, we want to know how many
neutrons the atom has. And to figure that out, we’ll look
at this number in the upper left. This is known as the mass number of
this atom. It’s equal to the number of protons
plus the number of neutrons in the atom.
Now if the mass number is equal to
the number of protons — we can call it 𝑁 sub 𝑝 — plus the number of neutrons —
we’ll call it 𝑁 sub 𝑛 — then we can see that if we subtract from that number, the
number of protons, then what we’ll get overall is the number of neutrons.
We can see from the chemical symbol
of this nitrogen atom that this number is 14 and that this number is seven. When we perform this subtraction,
we get a result of seven. And that’s equal to 𝑁 sub 𝑛, the
number of neutrons in the atom. So if we were to draw in neutrons
in green, then we will complete our picture of the nucleus by drawing seven of those
in place. And that answers our second
question. The number of neutrons that this
nitrogen atom has is seven.
