00:01
All right, so if we know some things about an atom, we can figure out how many subatomic particles it might have.
00:10
Okay, so if we know, for instance, the atomic number, the atomic number will tell us the number of protons that a particular atom has.
00:26
If it's a neutral atom, it will tell us the number of electrons as well, but if it's an ion, it won't.
00:32
Okay, so it always tells you the number of protons.
00:38
The mass number tells you the number of protons plus the number of neutrons.
00:50
So the number of particles inside the nucleus.
00:56
Now the mass number minus the atomic number.
01:03
Now let's look.
01:05
Mass number tells us protons plus neutrons, right? so we have protons plus neutrons...