Atomic Structure

Chapter 4

Lesson 1

Early Models of the Atom

First: A definition:

An atom is the smallest particle of an element that retains its identity in a chemical reaction. (p101)

Early Models of the Atom

Democritis (before 370 BC): Atoms are indivisible Atoms are indestructible

Not possible to do experimental research on atoms due to lacking technology.

Early Models of the Atom

Dalton’s Atomic Theory (Between 1766-1844)

All elements are composed of tiny indivisible particles called atoms.

Atoms of the same element are identical. The atoms of any one element are different from those of any other element.

Early Models of the Atom

Dalton’s Atomic Theory (Between 1766-1844)

Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds.

Chemical reactions when atoms are separated, joined, or rearranged. Atoms of one element are never changed into another element as a result of a chemical reaction.

Early Models of the Atom

Even though some parts of Dalton’s theory have been disproven, its pretty good knowing that he died more than 30 years before Edison invented electric lightbulbs.

Early Models of the Atom

A question: What happens to atoms in a chemical reaction

according to Dalton’s Theory?

Sizing up the Atom

A pure copper penny contains about

2.4 x 1022 atoms (the human population in the universe is 6 x 109 people

A line of 6x109 copper atoms would be only 6cm (2 3/8 inches) long.