Chapter 4 Chem Vocab

Atom

a basic unit of matter that cannot be broken down by normal chemical reactions

laws of conservation of mass

states that during a chemical reaction, the total mass of the products must be equal to the total mass of the reactants

law of definite proportions

a given compound always contains exactly the same proportion of elements by mass

Law of Multiple Proportions

whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers

Democritus

Greek philosopher that said all matter is made of tiny particles called "atomos" or atoms

John Dalton

formulated an atomic theory based on the law of conservation of mass, the law of definite proportions, and the law of multiple proportions

cathode ray tube

a device in which an electric current was passed through gases at low pressure

Electrons

negatively charged subatomic particles

Protons

positively charged subatomic particle

Neutrons

subatomic particles that have no charge (or neutral charge)

J. J. Thompson

discovered the electron and developed the plum pudding model

James Chadwick

Discovered the neutron in 1932

atomic model

scientists' representation of an atom determined by experiment and indirect observation

Nucleus

the tiny, dense, central core of the atom and is composed of protons and neutrons.

Ernest Rutherford

discovered the nucleus using the gold foil experiment

atomic number (Z)

the number of protons in the nucleus of each atom of that element

mass number

the total number of protons and neutrons in an atom

isotopes

atoms that have different mass numbers due to a change in the number of neutrons.

nuclide

the nucleus of a given isotope of an element

Ion

charged particle that has either more or fewer electrons than protons

Charge

A measure of the extra positive or negative particles that an object has.

Electron Cloud

a region around the nucleus of an atom where electrons are likely to be found