1. 1.1-1.2 Nature of Chemistry and Atomic Structure
Unit 1

2. What is Chemistry?
-study of matter and its interactions.
-involves experimenting in the macroscopic world and theorizing about the microscopic world

3. Types of Knowledge
Empirical knowledge- knowledge that comes from investigation and observation
Theoretical knowledge - knowledge that explains scientific observation.
-based on ideas created to explain observation

4. Theory vs.Law
Theory - an explanation or model based on observation, experimentation and reasoning.
-best understanding of why something happens
-allows us to predict future events
-evolve and change over time as new information is collected
Law – a generalized rule to explain a body of observations either as a statement or mathematical equation
-has been proven over and over (has stood the test of time)

5. The International Union of Pure and Applied Chemistry (IUPAC)
a council that was established in 1919 to regulate standards and procedures in chemistry so that information in the field can be understood worldwide

6. 1.2 Atomic Structure What is an ATOM?
-smallest possible particle of an element

7. Atomic Models
Model - an attempt to use familiar ideas to describe things in a visual way. There have been several models of the atom.
TIMELINE OF ATOMIC MODELS
Greek Philosophers
-matter can be subdivided into tiny particles called atomos (cannot be cut or indivisible)

8. Democritus
-atoms have different sizes, are in constant motion, and are separated by empty spaces
-simply a round sphere with no electrons, protons, or neutrons
Aristotle
-all matter is composed
of four essential
substances: earth , air,
water, and fire

9. Dalton
-atoms are solid spheres like billiard balls
He said:
a. all matter is made up of tiny, indivisible particles called atoms
b. all atoms of an element are identical
c. atoms of different elements are different
d. atoms are rearranged to form new
substances in chemical reactions but they are never created or destroyed (Law of
conservation of mass)
*doesn't explain how things acquire electrical charge

10. Thomson
-used the cathode ray tube to discover the electron
-plum pudding model: electrons are small negative particles evenly spaced in a positive sphere

11. Rutherford
-aimed tiny positive alpha particles at gold foil and measured how many alpha particles deflected off the foil on a fluorescent screen and found most were absorbed by the foil and only a few were deflected
-nuclear model: an atom contains a small, dense positive central nucleus.
-The positive particles are protons.
-The nucleus is surrounded by mostly empty space occupied by electrons.
-predicted the existence of the neutron (same mass as the proton but has no charge)

12. Chadwick
-confirmed the existence of the neutron
Bohr
-observed that hydrogen emitted light when excited by energy
-realized hydrogen has a unique spectrum
-planetary model: electrons orbit the nucleus in definite energy levels and can jump between energy levels. Each energy level holds a specific number of electrons. -The outer orbit of electrons is called the valence shell.

13. Bohr’s Model

14. Summary of Subatomic Particles
The mass of atomic particles is so tiny that IUPAC has decided to measure the mass of atoms in atomic mass units (U). The atomic mass unit is 1/12 the mass of a carbon -12 atom
PARTICLE LOCATION CHARGE MASS
Electron Orbit
Proton Nucleus U
Neutron Nucleus U

15. #of protons = atomic number(Z)
Bohr -Rutherfold Diagrams
#of protons = atomic number(Z)
# of electrons = # of protons= atomic number
#of neutrons = mass(A)-atomic number
Rule to fill orbits for elements #1-18:
level electrons maximum
level electrons maximum
level electrons maximum

16. TRY THIS: Draw a Bohr diagram for Calcium
Atomic Mass 40 20
P= 20
N= 20
E= 20
Ca Standard Atomic Notation
Atomic Number

17. Homework:
P. 10 #4,6
P.16 #1-2,5,10