Chemistry HL - Atoms: The Building Blocks of Matter - Chapter 3

Vocab. & Review

Democritus

a Greek philosopher who lived around 400 B.C. / was the first person to use the term “atom”

"Indivisable”

the Greek meaning of “atom”

Law of Conservation of Mass

Within the invention of an accurate balance scale, chemists began to measure the masses of the chemicals they were working with, leading to the discovery of this

Atom

smallest particle of an element that retains the properties of that element

Atomic Number

the number of protons an atom contains

Isotopes

atoms of the same element that have different masses

Nuclide

a general term for the specific isotope of an element

The Average Atomic Mass

the weighted average of the atomic masses of the naturally occurring isotopes of an element

Mole

the amount of a substance that contains as many particles as there are atoms in 12 grams of Carbon-12

Avagardo’s Number

the number of particles in the mole (6.022 × 10²³)

(John) Dalton

proposed an explanation for the law of conservation of mass, the law of definite proportions, and the law of multiple proportions / he reasoned that elements were composed of atoms and that only whole numbers of atoms can combine to form compounds / credited with the discovery of atoms

(JJ) Thomson

discovered electrons

(Ernest) Rutherford

discovered the nucleus through the Gold Foil Experiment

(Amedeo) Avagardo

determined the number of particles in the mole

Aristotle

claimed that all matter was made up of one continuous particle rather than atoms

Law of Definite Composition

states that each time a compound is formed, it will contain the same elements in the same ratio

Law of Multiple Proportions

states that if two or more compounds are composed of the same elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers

Electron

very large charge to mass ratio / smallest

(James) Chadwick

discovered neutrons

Proton

equal to neutron (size) / slightly smaller

Neutron

equal to proton (size) / slightly larger

Nuclear Forces

short range Proton-Neutron, Proton-Proton, and Neutron-Neutron forces that hold the nucleus together

Relative Atomic Mass

the Carbon atom is used as a standard form of measurement to establish the mass of all other atoms