1

Slide 1 of 18

Chemistry 4.1

© Copyright Pearson Prentice Hall

Slide 2 of 18

Defining the Atom

The lab technician shown here is using a magnifying lens to examine a bacterial culture in a petri dish. When scientists cannot see the details of what they study, they try to obtain experimental data that help fill in the picture.

4.1

2

Slide 3 of 18

© Copyright Pearson Prentice Hall

Defining the Atom > Early Models of the Atom

Early Models of the Atom

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

• Philosophers and scientists have proposed many ideas on the structure of atoms.

4.1

© Copyright Pearson Prentice Hall

Defining the Atom >

Slide 4 of 18

Early Models of the Atom

Democritus’s Atomic Philosophy

How did Democritus describe atoms?

Democritus

4.1

3

© Copyright Pearson Prentice Hall

Slide 5 of 18

Defining the Atom > Early Models of the Atom

Democritus believed that atoms were indivisible and indestructible.

Democritus’s ideas were limited because they didn’t explain chemical behavior and they lacked experimental support.

4.1

Slide 6 of 18

© Copyright Pearson Prentice Hall

Defining the Atom > Early Models of the Atom

Dalton’s Atomic Theory

How did John Dalton further Democritus’s ideas on atoms?

4.1

4

Slide 7 of 18

© Copyright Pearson Prentice Hall

Defining the Atom > Early Models of the Atom

By using experimental methods, Dalton transformed Democritus’s ideas on atoms into a scientific theory.

The result was Dalton’s atomic theory.

4.1

© Copyright Pearson Prentice Hall

Slide 8 of 18

Defining the Atom > Early Models of the Atom

All elements are composed of tiny indivisible particles called atoms.

4.1

5

© Copyright Pearson Prentice Hall

Slide 9 of 18

Defining the Atom > Early Models of the Atom

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

4.1

© Copyright Pearson Prentice Hall

Slide 10 of 18

Defining the Atom > Early Models of the Atom

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

4.1

6

© Copyright Pearson Prentice Hall

Slide 11 of 18

Defining the Atom > Early Models of the Atom

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

4.1

© Copyright Pearson Prentice Hall

Defining the Atom >

Slide 12 of 18

Sizing up the Atom

Sizing up the Atom

What instruments are used to observe individual atoms?

4.1

7

© Copyright Pearson Prentice Hall

Slide 13 of 18

Defining the Atom > Sizing up the Atom

Despite their small size, individual atoms are observable with instruments such as scanning tunneling microscopes.

4.1

Slide 14 of 18

© Copyright Pearson Prentice Hall

Defining the Atom > Sizing up the Atom

Iron Atoms Seen Through a Scanning Tunneling Microscope

4.1