Chapter 3

The Structure of Matter

Greek Atom

• earliest recorded reference to the atom

• thought that all matter was composed of 4 elements (earth, water, air, and fire) and modified by 4 essences (wet, dry, hot, and cold).

• atom meant indivisible to them

118; 92; 26

Currently, ____ substances or elements have been identified; ___ naturally occurring, and the additional ___ have been artificially produced.

Atom

smallest particle that has all the properties of an element.

Dalton Atom

• 19th century

• found that atoms were different based on atomic mass

• element composed of identical atoms that reacted the same way chemically were alike.

• led to Mendeleev’s periodic table of elements

• Introduced the “hook and eye theory” which is that atoms of a similar atomic mass naturally latch on to each other.