Atomic Theories

Did Dan just realize beryllium’s metal?

What did the element say when he got into a fight?

Let me atom

Democritus• Greek philosopher• the originator of a theory on

atoms• He said atoms are the smallest

indivisible bodies from which everything else is composed

Dalton• Developed the first useful atomic

theory

• His theory was comprised of 4 postulates

The postulates

1. All matter consists of tiny particles called atoms

2. Atoms are neither created nor destroyed (based on???)

The postulates (cont.)3. All atoms of a given element

are identical and different from any other element

4. A given compound always has the same relative numbers and kinds of atoms

J.J. Thomson• Discovered that the atom has a

substructure using a cathode ray

• Discovered a negatively charged particle and named it the electron

Cont.

• Couldn’t calculate the mass of an electron but figured out the ratio of its charge to its mass

T-money cont. • His model is called the mint choc.

chip model because

• The atom was electrons surrounded by a soup of positive charge to balance the electron's negative charge, like chips surrounded by mint ice cream.

Ernest Rutherford• Performed the gold foil experiment

to discover the positively charged nucleus

• He shot a beam of alpha particles at a piece of gold foil, while most went through, there were some that got scattered in every direction

• Pg. 104

Are you Bohr’d yet?

• Niels Bohr’s model depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus

• Improvement on Rutherford's model

Modern Atomic Theory• Nucleus lies in the center of the

atom• Electrons do not orbit in well-

defined paths, rather they can be predicted in an area called an electron cloud

Something to break the monotony

•When they broke open molecules, they found they were only stuffed with atoms. But when they broke open atoms, they found them stuffed with explosions.

Subatomic Particles

Proton-

Neutron-

ELECTRON-

Proton

• positive

• found in the nucleus

• has the mass of 1 amu

Joke 1• A Hydrogen atom runs up to two other

atoms yelling and waving his arms. "Help! A mugger just stole my electron!" One of the other atoms looks him over and asks, "Are you sure?" The first replies: "I'm positive!"

Neutron

• Neutral

• found in the nucleus

• has the mass of 1 amu

Joke 2

• A neutron walks into a bar and orders a drink. When he attempts to pay, the bartender looks at him and says, "For you, no charge."

ELECTRON

• Negative

• found outside the nucleus

• its mass is so small comparably that it is considered negligible

Joke 3

• SUBATOMIC PARTICLE STORE

The subatomic particle store had a sale last week.

Electrons: $0.10Protons: $0.10Neutrons : free of charge

Atomic Number

•# of protons

•Atoms are neutral so the # of protons must equal ________

•The whole number found in the element box

Atomic Mass

•Number of protons + number of neutrons

•Measured in AMUs (Atomic mass units)

•Where are the electrons?

Isotopes•Atoms that have the same

number of protons but different number of neutrons

•Do isotopes have the same charge?

•Do isotopes have the same masses?

Isotope notation

                

Isotope Notation decoded

•"X" represents the atom's elemental symbol. 

•"A“--The mass number, (located in the upper left-hand corner)

•"Z“-- The atomic number (found in the lower left-hand corner)

Last joke

•Q: What did the thermometer say to the graduated cylinder?

•A: "You may have graduated but I've got many degrees"