Transcript atoms 2 123

Review of Atomic Theory History
- Introduction to Atoms
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
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.
The electron Energy Levels fill in this order:
1st level- holds up to 2 electrons
2nd level- holds up to 8 electrons
3rd level- holds up to 18 electrons
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).
- Introduction to Atoms
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
- Organizing the Elements
Finding Data on Elements
Each square of the periodic table includes an element’s
atomic number, chemical symbol, name, and atomic mass.