1. A. Structure of the Atom Chemical Symbols Subatomic Particles
2. Atomic Structure
A. Structure of the Atom
Chemical Symbols
Subatomic Particles

2. Metal that forms bright blue solid compounds.
Chemical Symbols
Capitals matter!
Element symbols contain ONE capital letter followed by lowercase letter(s) if necessary.
Metal that forms bright blue solid compounds.
Co vs. CO
Poisonous gas.

3. Subatomic Particles in a neutral atom Most of the atom’s mass.
NUCLEUS
ELECTRONS
in a neutral atom
PROTONS
NEUTRONS
NEGATIVE CHARGE
POSITIVE CHARGE
NEUTRAL CHARGE
Most of the atom’s mass.
Atomic Number
equals the # of...

4. B. Masses of Atoms Atomic Mass Mass Number Isotopes

5. Atomic Mass atomic mass unit (u) 1 u = 1/12 the mass of a 12C atom
1 proton = 1 u 1 neutron = 1 u
1 u = 1.67  g
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6. Mass Number Sum of the protons and neutrons in the nucleus of an atom.
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Always a whole number.
# of neutrons = mass # - atomic #

8. Isotopes Mass # Atomic #
Atoms of the same element with different numbers of neutrons.
Isotope symbol:
Mass #
Atomic #
“Carbon-12”

9. Isotopes
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10. Isotopes Average Atomic Mass reported on Periodic Table
weighted average of all isotopes
Avg.
Atomic
Mass

11. Isotopes
EX: About 8 out of 10 chlorine atoms are chlorine-35. Two out of 10 are chlorine-37.
Avg.
Atomic
Mass
35.4 u

12. 3. Electron Cloud Model Orbital Energy Levels Bohr Model Diagrams

13. Orbital Region where there is 90% probability of finding an electron.
Can’t pinpoint the location of an electron.
Density of dots represents degree of probability.

14. Orbital
Orbitals have different shapes.

15. Energy Levels Electrons can only exist at certain energy levels.
Low energy levels are close to the nucleus.
Each energy level (n) can hold 2n2 electrons.

16. Bohr Model Diagrams
Simplified energy levels using Bohr’s idea of circular orbits.
Lithium
Atomic #: 3
Mass:
# of p: 3
# of e: 3
# of n: 4 e- e- p n e-