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things that might be important from chapter 2

Democritus and early Greek philosophers

thought the material would must be made of tiny invisible particles called atomos meaning "indivisible or uncuttable"

Isaac Newton

favored the idea of atoms

John Dalton

created Dalton's atomic theory

Dalton's atomic theory-1

Each element is composed to extremely small particles called atoms

Dalton's atomic theory-2

All atoms of a given element are identical to one another in mass and other properties, but the atoms of one element are different from the atoms of all other elements.

Dalton's atomic theory-3

The atoms of one element cannot be changed into atoms of a different element by chemical reactions; atoms are neither created nor destroyed in chemical reactions

Dalton's atomic theory-4

Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms


smallest particles of an element that retain the chemical identity of the element

law of conservation of mass

The total mass of materials present after a chemical reaction is the same as the total mass present before the reaction.

law of multiple proportions

if two elements A and B combine to form more than one compound, the masses of B that can combine with a given mass of A are in the ratio of small whole numbers.

subatomic particles

the atom is composed of these smaller parts

particles with the same charge

repel one another

particles with unlike charges

attract one another

cathode rays

radiation produced from the negative electrode when high voltage was applied to partially excavated tubes


negative electrode

J. J. Thomson

observed cathode rays and discovered the electron, "plum-pudding model"

Robert Millikan

oil-drop experiment; discovered the mass of an electron


the spontaneous emission of radiation

Henri Becquerel

studying uranium and discovered it spontaneously emits radiation

Marie Curie

with husband began experiments to isolate radioactive components of uranium

Ernest Rutherford

revealed three types of radiation: alpha, beta, gamma; "gold foil experiment"

"plum-pudding model"

J. J. Thomson proposed that the atom was a uniform sphere with embedded electrons


positively charged particles in the nucleus


neutral particles in the nucleus

James Chadwick

discovered neutrons

electronic charge

1.602 x 10⁻¹⁹ C; all charges of subatomic particles are represented as multiples of this charge

atomic mass unit

1.66054 x 10⁻²⁴ g = 1 amu


A°, 10⁻¹⁰ m

atomic number

the number of protons in any element (subscript)

number of electrons

same as number of protons

mass number

total number of protons plus neutrons in an atom (superscript)


atoms with identical atomic numbers but different mass numbers

average atomic mass

found using masses of isotopes and relative abundance on earth

metallic elements or metals

left side and middle of periodic table

nonmetallic elements or nonmetals

separated from metals by a diagonal step ladder in the periodic table


lie along the line between metals and nonmetals in the periodic table


assembly of two or more atoms tightly bound together

chemical formula

shows the elements in the compound and the ratio of atoms

diatomic molecule

made up of two atoms

molecular compounds

composed of molecules of more than one type of element

molecular formulas

actual numbers and types of atoms in a molecule

empirical formulas

lowest ratio of elements in a molecule

structural formula

shows which atoms are attached within a molecule


a charged particle


negatively charged particle


positively charged particle

polyatomic ions

consist of atoms joined as in a molecule with a net charge

ionic compound

compound that contains both positively and negatively charged ions

chemical nomenclature

system for names and formulas of compounds


only contain carbon and hydrogen


hydrocarbons that contain carbon atoms that are bonded to four other atoms

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