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Chemistry Study Guide #2


Enrico Fermi



Chemistry Review 2

Famous Scientists 9/19

Democritus- A Greek philosopher born in 460 BC. Formed the first idea of the atom- “atomos,” or “no cut”- something that can be broken down no further. Lived to be 110 years old.

Sir Isaac Newton- 1642-1727. Made advances in mathematics, optics, physics and astronomy. In 1704 proposed a mechanical universe with small solid masses in motion. Also came up with the three laws of motion.

John Dalton- 1766-1844. The Father of Chemistry. A teacher since age 12. Made over 200,000 atmospheric experiments. Was the first to describe color- blindness (Daltonism). Atom idea- a small, hard sphere.

JJ Thompson- 1856-1940. Discovered the electron using a Cathode Ray Tube. Atom idea- Plum Pudding Theory.

RA Millikan- 1868-1953. Determined the charge of an electron was 1.6 x 10 to the –19C using an oil drop experiment in 1909.

Rutherford- 1871-1937. Discovered the nucleus in 1911 with the gold foil experiment. Born in New Zealand. Coined the terms Alpha, Beta, and Gamma Rays. Atom idea- similar to the plum pudding theory but with a nucleus.

Niels Bohr- 1885-1962. Danish physicist who came up with the orbital theory.

Shrodinger- 1887-1961. In 1930 came up with “wave mechanics,” continuous clouds. Related to quantum mechanics. “Schrodinger’s cat” theory.

James Chadwick- 1891-1974. In 1932 discovered the neutron with help of Irene Joiliot-Curie, using Beryllium.

Enrico Fermi- 1901-1974. Produced the first nuclear chain reaction in University of Chicago’s Metallurgical Lab. Was forced to help develop the atomic bomb, which was first tested July 16, 1945.

Atoms and Elements 9/22

Law of Conservation of Mass- Mass of reactants = the mass of products. “matter can be neither created nor destroyed.” Created by Antoine Lavoisier.

Law of Definite Proportions- different samples of any pure compound contain the same elements in the same proportions by mass. Created by John Dalton.

Law of Multiple Proportions- the Mass ratio for any of the elements in a compound can be expressed as small whole numbers. Created by John Dalton.

The Atom 9/23

Particle Charge Mass (g) Mass (AMU)

Protons p+ +1 1.6727 x 10 –24 1.007316

Neutrons n 0 1.6750 x 10 –24 1.008701

Electrons e- -1 9.110 X 10 –28 .000549

1 AMU (aka Dalton, Da) = 1.67377 x 10 –24 g

Nucleus in atom is the size of a marble in a football stadium.

Atomic Theory- atoms are the building blocks of elements

Periodic Table

Groups

Periods

Isotope- Atom w/ diff # neutrons

Quantum Theory 9/25

Orbitals- regions of space where there is a high probability of finding an electron

Energy Level Max Electons L

S 2 0

P 6 1

D 10 2

F 14 3

Orbital Representation 9/26

The outer electrons are the most important because they are the most likely to move

Orbital Representation- little boxes

Electron Configuration- Shorthand

Aufbau Diagram- Box chart on yellow sheet

Quantum #s- use orbital representation to find them fast

N Quantum #- Principal energy level. N = 1-7. Number of end energy level in EC

L Quantum #- Refers to the shape of orbital s-f is 0-3

Ml- refers to which box- -l to l

Spin Quantum #- last arrow pointing up, is ˝. Last arrow pointing down, is -1/2.

Electrons in Atoms 9/30

Aufbau Principle- electrons enter first energy level first

Pauli Exclusion Principle- there can be only up to two electrons per orbital/box. They must have different spins

Hund’s Rule- When electrons occupy orbitals of equal energy, they don’t pair up until they have to.

Light

- Light is a kind of electromagnetic radiation

- Includes many kinds of waves

- Speed of light- 2.998 10 to the 8th m/s = c

Wave length- measured by crests, troughs, or nodes. Abbreviated by Greek Lambda .

Frequency- # waves/ second. Measured in hertz. C = /v

White light is made of all colors. Prism splits.

Atomic Spectrum

- Each element gives off its own characteristic colors

- Can be used to identify the atom

- How we know what stars are made of

- Electrons move to different energy levels- give off energy as light when fall back

Ground State- lowest energy level

Heisenberg Uncertainty Principle- it’s impossible to know exactly the location and velocity of a particle.

Book Chapter 3

3-1

Dalton’s Atomic Theory- #s 1 and 2 proved false

1. All matter is made of indivisible and indestructible atoms

2. All atoms of a given element are identical in thrir physical and chemical properties.

3. Atoms of different elements differ in their physical and chemical properties.

4. Atoms of different elements combine in simple whole-number ratios to form compounds.

5. Chemical reactions consist of the combination, separation, or rearrangement of atoms.

Avogrado’s constant- the number of particles in a mol (6.022137 x 10 to the 23)

3-2

JJ Thomson’s Cathode Ray Experiment- discovered electrons

Anode- plate attached to the positive end of a power source

Cathode- negative plate

Cathode Rays are used in TVs, computer and radar screens, and oscilloscopes.

Alpha particles- positively charged

Coulomb’s Law- the closer two charges come together, the greater the force between them. Factor increases by 4 as distance decreases by 2

Strong force-keeps stable nuclei, w/ neutrons & protons together despite proton’s repulsing each other.

3-3

Frequency x wavelength = speed of light

Line- emission spectrum- colored lines produced by prism & charged element

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