Gen Chem. (July 22)

Law of Conservation of of Mass, Law of Definite Composition, and Law of Multiple Proportions

3 Laws of Matter

Law of Conservation of Mass

It states matter can neither be destroyed created or destroyed

Law of Definite Composition

It states that any sample of a compound will invariably have the same proportions by mass of its constituent elements.

Law of Multiple Proportions

It states that if two elements can combine to form more than one compound, the masses of one elements that combine with a mass of the other element are in fixed ratios of whole numbers.

John Dalton

A chemist and school teacher in England, revived and revised Democritus’ ideas and turned them into a scientific theory. (1803)

Democritus

An ancient Greek Philosopher (400BC).

Proposed all matter is made of tiny, indivisible, or uncut particles (atomos)

Compounds

Are composed of atoms of at least two different elements, and the ratio of each element is an integer of a simple fraction.

Chemical Reaction

Is a result from the rearrangement of the atoms of reacting substances, giving new combinations of atoms.

Electron, Proton, and Neutron

The Subatomic Particles:

Electron

The first subatomic particle to be discovered.

Cathode Ray Tube

The instrument/device that was used to discover the first ever subatomic particle.

Cathode

The negative electrode:

Anode

The positive electrode

J.J. Thomson

An Englishmen who discovered the electron

Proposed the Plum Pudding Model

Concluded that the cathode ray must be composed of negatively charged particles in all atoms.

Robert Millikan

Determined the charge of an electron (9.1094 × 10 ^ -28g)

Performed the oil drop experiment

Oil Drop Experiment

It used x-rays to knock electrons off atoms in oil droplet

Ernest Rutherford

Discovered positive particles (called protons) while studying nitrogen molecules and concluded that it is heavier than electrons.

Performed an experiment on the atom using alpha particles.

Hans Geiger and Ernst Marsden

The assistants in the Gold Foil Experiment.

They came up with a device that shoots rays of alpha particles at a thin sheet of gold.

Plum Pudding Model

An old model of the atom featuring a sphere of positive charge w/ negative electrons embedded inside it.

Proposed by JJ Thomson after he discovered the first subatomic particle

Nuclear Model

The new model of the atom; It is described with a dense… positively charged nucleus and tiny pieces of negatively charged particles orbiting around it.

James Chadwick

Credited as the discoverer of the neutron

Bombarded a thin sheet of beryllium with alpha particles

It is described as being almost as heavy as protons

Atomic Number

It is equal to the number of protons or ”electrons” of an atom

Mass Number

It is equal to the number of protons or “electrons” and neutrons

Isotopes

Atoms that have the same number of protons but different number of neutrons

Deuterium

A hydrogen element with 1 proton and 1 neutron

Tritium

A hydrogen element with 2 neutrons and 1 proton

Nitrogen-15

A naturally occurring isotope of nitrogen. It has uses in medicine and in biology.

Carbon-14

An isotope of carbon; It is produced when nitrogen in the atmosphere is hit by cosmic rays.

Uranium-235

Used in nuclear reactors to produce electricity.

Uranium-238

It is found in smoke detectors