Unit 3 - Part II Exam Review: Atomic Structure, Isotopes, Ions, and Scientists

Vocabulary practice flashcards covering atomic notation, isotopes, ions, and major atomic theory scientists for the Unit 3 - Part II Exam.

Isotope

A different form of an element or atom with a different number of neutrons.

Average Atomic Mass Formula

$$\frac{(\text{Average mass of isotope} \times \%\,\text{Abundance})_1 + (\text{Average mass of isotope} \times \%\,\text{Abundance})_2 + \dots}{100}$$

Nuclear Isotope Notation ($^A_Z\text{X}$)

A notation format where $\text{X}$ is the chemical symbol, $A$ is the mass number ($A = Z + N$), and $Z$ is the atomic number (number of protons).

Mass Number ($A$)

The total number of protons and neutrons in an atom, represented by the formula $A = Z + N$.

Atomic Number ($Z$)

The number of protons in an atom.

Anion

A negatively charged ion formed when an atom gains electrons.

Cation

A positively charged ion formed when an atom gives away (loses) electrons.

Group 18 (Noble Gases)

Elements that do not form ions because they already possess a full outer shell of electrons.

Democritus

Atoms are indivisible. Atoms are all the same in all matter, but they differ in size and shape. Discovered that all matter is made up of particles called atomos.

Millikan

Performed the oil-drop experiment. Measure the charge of an electron. 

J.J. Thomson

Discovered the electron. Made a model of the atom called the “plum-pudding model”. Believed that electrons were embedded in the surface of an atom

Ernest Rutherford

Discovered the proton and the positively charged nucleus. He also discovered that the majority of an atom is made up of empty space through his gold-foil experiment. 

Niels Bohr

Discovered that the positively charged nucleus is surrounded by electrons in rings. Came up with the planetary model of atoms. 

John Dalton

Came up with the billiard-ball model of the atom. Father of the atomic theory:  Different atoms have different chemical properties. All matter is made up of atoms. Law of definite proportions: atoms combine in whole-number ratios to form compounds.

Law of Definite Proportions

A principle associated with Dalton stating that atoms combine in whole-number ratios to form compounds.

James Chadwick

Scientist who discovered that the neutron exists in the nucleus.