Atoms: The Basic Units of Matter
Inside an Atom
Atomic Structure
An atom has a dense nucleus at the center and electrons around it. The nucleus contains protons and neutrons, while electrons occupy regions outside the nucleus.
Subatomic Particles
| Particle | Charge | Location |
|---|---|---|
| Proton | +1 | Nucleus |
| Neutron | 0 | Nucleus |
| Electron | -1 | Outside nucleus |
A Helpful Picture
Think of the nucleus as a tiny center and electrons as a fast-moving cloud around it. This is a model, not a tiny solar system.
Atomic Identity
Elements and Atomic Number
The number of protons in an atom is called the atomic number. It tells us which element the atom is. For example, all carbon atoms have protons.
Which particle determines the identity of an element?
The number of protons defines the element.
Correct answer: Proton
What is the center of the atom called?
The nucleus is the central region containing protons and neutrons.
Correct answer: nucleus
Which particle has a negative charge?
Electrons carry negative charge.
Correct answer: Electron
Reading an Atom
-
1
Count the protons to identify the element.
-
2
Look at the electrons to understand bonding behavior.
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3
Consider neutrons for mass and isotopes.
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4
Use the structure to predict chemical properties.