Review of Atomic Theory History

Structure of an Atom

A carbon atom consists of protons and neutrons in a nucleus that is surrounded by electrons.

- Introduction to Atoms

Models of Atoms

- Introduction to Atoms

For over two centuries, scientists have created models of atoms in an effort to understand why matter behaves as it does. As scientists have learned more, the model of the atom has changed.

1st level- holds up to 2 electrons

2nd level- holds up to 8 electrons

3rd level- holds up to 18 electrons

The electron Energy Levels fill in this order:

18

8

2

New Material….

HOW TO DETERMINE NUMBER OF EACH OF THE THREE MAIN PARTICLES:

PROTONS: From the Periodic Table, the “Atomic Number” identifies the number of protons

ELECTRONS: Same as the number of protons (for now) to keep the atom neutrally charged

NEUTRONS: mass # - atomic #

(because the mass # is the number of protons plus neutrons)

Isotopes

-not all atoms of an element have the same number of neutrons (but they ALWAYS have the same number of protons—based on atomic number).

-Atoms of the same element that have different numbers of neutrons are called isotopes

(i.e.- Carbon 12, Carbon 13, and Carbon 14).

Isotopes

Atoms of all isotopes of carbon contain six protons, but they differ in the number of neutrons. Carbon-12 is the most common isotope.

- Introduction to Atoms

Review Questions

Structure of an Atom

Q. What particles are in the center of the atom?

A. Protons and neutrons

Q. What particles move around the outside of the nucleus?

A. Electrons

- Introduction to Atoms

Finding Data on Elements

Each square of the periodic table includes an element’s atomic number, chemical symbol, name, and atomic mass.

- Organizing the Elements