This document defines key chemistry concepts including atoms, elements, compounds, and their components. Atoms are the basic building blocks of matter and consist of a nucleus containing protons and neutrons surrounded by electrons. Elements are pure substances made of only one type of atom, while compounds consist of two or more elements bonded together. The number of protons determines the atomic number of an element.

1. Peterson

2.  Atom – basic building block of all matter.
Examples = He H2O Salt Water Italian Salad Dressing

3.  Element – substance that consists of only
one type of atom.
Example = O or Oxygen
 Molecule may have one, two or more…
Example = O2 or Oxygen
 Compound – substance that consists of more
than one type of element.
Example = CO2 or Carbon Dioxide

4.  Atoms
 Nucleus – small, heavy part of the atom
 Electron Cloud – large, light weight part of the atom

5.  Nucleus –
 Neutrons No charge, Mass of 1 AMU
 Proton + charge, Mass of 1 AMU
 # protons = Atomic #
 Atomic mass = n + p+

6.  Electron Cloud –
 Electrons - charge, ~0 mass
 Determine bonding properties of substance!
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