Science 8 Reviewer: Matter, Elements, Periodic Table, and Atomic Structure

Vocabulary practice flashcards covering matter, elements, compounds, subatomic particles, historical contributors to the periodic table, periodic table organization, and neutron calculation formulas.

Pure Substance

Matter that has a fixed and definite chemical composition.

Element

A pure substance made up of only one kind of atom that cannot be broken down into simpler substances by chemical means.

Compound

A pure substance made up of two or more different elements chemically combined in a definite proportion that can be chemically separated into its elements.

Proton

A subatomic particle with a positive charge located in the nucleus.

Neutron

A subatomic particle with no charge located in the nucleus.

Electron

A subatomic particle with a negative charge located outside the nucleus.

Atomic Number

The number of protons in an atom, which determines the identity of an element.

Johann Wolfgang Döbereiner

The scientist who proposed the Law of Triads by grouping elements into sets of three with similar properties.

Law of Triads

A classification proposed by Johann Wolfgang Döbereiner grouping elements into sets of three based on similar properties.

John Newlands

The scientist who proposed the Law of Octaves by arranging elements according to increasing atomic mass and observing that properties repeated at regular intervals.

Law of Octaves

A concept proposed by John Newlands stating that elemental properties repeat at regular intervals when arranged in order of increasing atomic mass.

Dmitri Mendeleev

The scientist who developed an early periodic table arranged mainly by atomic mass and chemical properties, leaving blank spaces to predict undiscovered elements.

Henry Moseley

The scientist who demonstrated that elements should be arranged according to their atomic number, providing the basis for the modern periodic table.

Period

A horizontal row in the periodic table; there are $7$ horizontal periods.

Group

A vertical column in the periodic table; there are $18$ vertical groups.

Representative Elements

Elements generally found in Groups $1$-$2$ and $13$-$18$ of the periodic table.

Transition Elements

Elements found in the central block of the periodic table, such as Gold (Au), Iron (Fe), and Copper (Cu).

Inner-Transition Elements

Elements found in the two rows placed below the main body of the periodic table, consisting of Lanthanides and Actinides.

Metals

Elements mostly found on the left and center of the periodic table that are usually shiny, malleable, ductile, and good conductors of heat and electricity.

Nonmetals

Elements mostly found on the right side of the periodic table that are poor conductors, may be dull, brittle when solid, and frequently gases at room temperature.

Metalloids

Elements generally found along the stair-step boundary that possess properties of both metals and nonmetals.

Mass Number

The total sum of protons and neutrons in an atom: $\text{Mass Number} = \text{Protons} + \text{Neutrons}$.

Number of Neutrons Formula

The mathematical relationship used to calculate neutrons in an atom: $\text{Number of Neutrons} = \text{Mass Number} - \text{Atomic Number}$.