Chemistry / Unit 2: Atomic Structure
2.2 Subatomic Particles
Notes
Atoms are made of three main particles.
| Particle | Charge | Relative mass (amu) | Location |
|---|---|---|---|
| proton | +1 | 1 | nucleus |
| neutron | 0 | 1 | nucleus |
| electron | -1 | about 1/1840 | outside the nucleus |
- Nearly all the mass of an atom is in the nucleus.
- A neutral atom has equal numbers of protons and electrons.
- The number of protons decides which element an atom is.
Practice
Which particle has almost no mass compared with the others?
An electron's mass is about 1/1840 of a proton's mass.
Which two particles are found in the nucleus?
Electrons are outside the nucleus.
What determines the identity of an element?
Every atom of carbon has 6 protons; change the proton count and you have a different element.
Ready for more? Take the Unit 2 test.