Gen chem chapter 2

J.J. Thompson

Discovered: Atom structure electrons.

How it works: Beam from cathode ray tube deflected toward positively charged plate. Atoms contain negatively charged particles with a constant mass/change ratio.

Plum Pudding: electrons distributed throughout a diffuse, positively charged sphere.

Robert Millikan and Harvey Fletcher

Discovered: Mass of Electron - Determined the mass and charge of an electron.

How it works: Oil drop experiment.

Henri Becqueral

Discovered: Radioactivity and the nuclear atom - Some materials produce invisible radiation, consisting of charged particles.

Mane and Prerre Curie

showed radiation consisted of small particles.

Ernest Rutherford

Discovered: The Atomic structure focusing on the nucleus

Bombard a thin gold foil with alpha particles to test Thomas model of the atom.

James Chadwick

Bombarded a thin sheet of beryllium with alpha particles; a very high radiation was emitted by the metal that was NOT deflected by either electric or magnetic fields.

• The radiation consisted of a 3rd subatomic particle called the neutrons.

Nucleus

The positively charged center of an atom containing nearly all of an atom’s mass.

Atomic Mass

Unit used to express the relative mass of an atom and subatomic particles.

Francis Aston

Positive Ray Analyzer

• 2 different types of neon gas exsists.
  Proved the exsistance of isotopes

Ne gas ions of different - strike the detector in different locations

Isotopes

Atoms of an element with the same number of protons but different number of neutrons.

Mass number on periodic table

total number of nucleons (protons + Neutrons)

Atomic Number

Number of protons in the nucleus which determines the identity.

Elemental Symbol

One or 2 letter symbols for an element

Average Atomic Mass

On periodic table, weighted average of mass of all isotopes of an element. Calculated by multiplying the natural abundance of each isotope by its mass in u then summing these products.

Natural Abundance

Proportion of a particular isotope usually expressed as a percentage relative to all the isotopes for that element in a natural sample.

Periodoc table

Horizontal rowas are called periods

Vertical Columns are called groups

Elements in the same group tend to have similar physical/chemical proerties

Elements are divided into 3 categories

• Metals

• Nonmetals

• Metalloid

Ionic Compounds

Consist of Cations (usually metals) and anions ( usually non-metals). Formulas for ionic compounds must always be neutral.

Consist of charged particles (ions) formed by transfer and electrons between atoms. Held together by cations and anions.

Cations

Named using the first element

Anion

is named by adding the -ide suffix to the name of the element

Law of multiple proportions

The ratio of the 2 masses of one element that reacts with a given mass of another element to form 2 different compounds is the ratio of 2 small whole numbers.

Molecular Compounds

Atoms are held together by covalent bonds. Composed of non-metals.

Covalent Bonds

Bond between 2 atoms created by the sharing of an electron.