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Every kind of matter is made of one or more elements.
An element is a substance that cannot be broken down into other substances by chemical or physical means. Elements are made of atoms.
An atom is the smallest particle of an element.
An atom consists of a nucleus surrounded by one or more electrons.
The nucleus is the tiny, central core of an atom. A nucleus contains protons and neutrons.
A proton is a positively charged particle. A neutron is a neutrally charged particle.
Electrons are particles with a negative charge that spin around the nucleus.
An atom is neutral because it contains equal numbers of protons and electrons.
Atomic number is the number of protons in a nucleus.
Atomic Mass Unit (amu) is used to measure the mass of a proton or neutron.
Valence electrons are the electrons that are farthest away from the nucleus. The number of valence electrons determines many properties of the atom.
Valence electrons form chemical bonds. A chemical bond is a force that holds atoms together.
Electron dot diagrams are used to show how many valence electrons an element has. It is made up of the symbol for an element surrounded by dots that represent how many valence electrons that element has.
Look here for a good website on atoms
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