Particles of Matter Notes

Particles of Matter

Objectives

• Explain how atoms are the particles that make up all matter.
• Describe Dalton’s Theory of Atoms.
• Identify chemical bonds as holding atoms together in molecules.

Vocabulary Words

• Atom
• Molecule
• Chemical Bond

Atoms

• Atoms are the smallest particles of an element.
• Democritus, a Greek philosopher, was one of the first people known to have developed the idea of atoms.
• Democritus suggested that atoms could not be divided any further and gave it the name atomos, which means uncuttable.

John Dalton

• In 1802, a British school teacher proposed the idea of an atomic theory.
• Dalton conducted experiments in a laboratory and used the evidence gathered to infer that atoms had certain characteristics.

The Atomic Theory

• Atoms can’t be broken into smaller pieces.
• In any element, all the atoms are exactly alike.
• Atoms of two or more elements can combine to form compounds.
• Atoms of each element have a unique mass.
• The masses of the elements in a compound are always in a constant ratio.

Atoms and Molecules Today

• Atoms combine and arrange to form different compounds.
• The basic particle of a compound is called a molecule.
• A molecule is a group of atoms that are joined together and act as a single unit.
• The force that holds two atoms together is called a chemical bond.
• Most atoms readily form chemical bonds with one or more other atoms.

Particle Model of Matter

• The particle model of matter is the consideration of matter in terms of atoms and molecules.
• It serves as a mental picture of how things actually work.
• It is useful because the model helps to explain many facts about the world around us.
• Scientists can explain all sort of properties of the elements from studying the atoms that compose them.