Chemistry Test

Aristole ~200BC:

-Described composition adn behavior of matter in terms of 4 qualities

1. Hot

2. Cold

3. Moist

4. Dry

Democritus ~2000 BC:

-Matter was made up of “Building Blocks” called '“atoms”

-The perecived texture, mass and color of a material was determined by the atom

Antoine Lavoisier ~1700s:

-Father of modern chemistry

-established the law of conservation of mass (Energy cannot be created or destroyed)

-There is no detectable change in the total mass of materials when they react chemically to form new chemicals

Joseph Proust:

-Law of definite propoptions(1794)

-”Elemnts combine in definite mass ratios to form compounds”

John Dalton:

-Was an english chemist and school teacher

-First organized the scientific theory of matter called the Atomic Theory (1808)

Atomic Theory:

1. Each element consists of Indivisible, minute particles called atoms

2. Atoms cannot be either created nor destroyed in a chemical reaction

3. All atoms of a given element are identical

4. Atoms chemically combine in definite whole number ratios to form compounds

5. Atoms of different elments have different masses

Joseph J. Thomson (1897):

-Cathode Ray Tube Experiment

-Discovered negative cathode particles/rays could be removed from metal plates

• The rays were later renamed electrons

-The Plum Pudding Model

Radioactivity vs Radiation

-Radioactivity described spontaneous changes in its nucleus of an atom that crates a different nuclide (isotope)

• Discovered by Henri Becquerel in 1896

-Radiation is the energy that is released as particles or rays in a radioactive decay

-Alpha particles are a type of radiation

• Sometimes reffered to as a “helium nucleus”

• Biggest type of Radiation

• Positive

Ernest Rutherford (1911)

-Gold Foil Experiment

-Used Alpha Particles to determine what was underneath the surface of teh atom

-Rutheford modified Thomson’s Model

• He still assume the atom is spherical but now the positive charge must be located at the center with a diffuse negative charge surrounding it

-The nuclear model of the atom

Atomic Structure:

-1886, Canal Ray Experiment

• Eugen Goldstein demonstrated that these rays were positive particles and called the canal rays

-The discovery of the proton is credited to Ernest Rutheford in 1917

-Sir James Chadwick discovered neutrons in 1932

Niels Bohr (1913):

-Bohrs model of the atom or reffered to as the planetary model of the atom

• Protons and Neutrons locateed in the Nucleus

• Electrons located in the Shells

Electrons:

-Heinsenburg Uncertainty Principle (1925)

-The Quantum mechanical model of the atom comes from the solution to Schrodinger’s equation

• Erwin Schrodinger (1926)

• Using he Bragile’s matter wave theory of the electron to develop and solve a probalisitc model of the atom using complex mathematical equation

• Solutions to the wave functions, give only the probability of finding an electron at a given point around the nucleus

Aufbau Procedure:

-The method of obtaining ground state configurations by filling lower energy orbitals first

Paul Exclusion Procedure

-No two electrons in an atom have the same set of 4 quantum numbers

Hund’s Rule

-For degenerate orbitals the lowest energy is when number of electrons with same spin is maximized

Valence Rule

-The valence electrons that exisit in the highest principle energy levels are involved with chemical reactions and bonding first.

Exception to the Rule

-Only applies to the d and f subshells due to the closeness in energy to the previous subshell

-If there are 1 openi s d take one from before