Atoms and Atomic Structure
The atom
What is an atom?
An atom is the smallest unit of an element that still keeps that element's identity. Atoms are the basic building blocks of matter.
Subatomic particles
Atoms contain three main subatomic particles: protons, neutrons, and electrons. Protons and neutrons are in the nucleus, while electrons move in the space around the nucleus.
Subatomic particles
| Particle | Charge | Location |
|---|---|---|
| Proton | +1 | Nucleus |
| Neutron | 0 | Nucleus |
| Electron | -1 | Outside nucleus |
Important idea
The number of protons defines the element. Change the number of protons, and you change the element.
Which particle has a negative charge?
Electrons carry a negative charge.
Correct answer: Electron
Where are protons found in an atom?
Protons are located in the nucleus along with neutrons.
Correct answer: In the nucleus
Atomic size and space
Atoms are mostly empty space. The nucleus is tiny compared with the full size of the atom, but it contains nearly all the mass.
What mainly determines an element's identity?
The number of protons is the atomic number and defines the element.
Correct answer: Number of protons