Introduction to Chemistry and the Periodic Table

Comprehensive vocabulary flashcards covering the classification of matter, the history and organization of the periodic table, element properties, and the rules for chemical formulas.

Dmitri Ivanovitch Mendeléev

The scientist who, in 1869, created the first accepted version of the periodic table by grouping elements by atomic mass and similar chemical properties.

Atomic Number

A unique number for each element that refers to how many protons an atom of that element has.

Atomic Mass

The average weight of an atom, derived by adding the number of protons and the number of neutrons.

Isotopes

Atoms of the same element that have a different number of neutrons than protons.

AMU (Atomic Mass Unit)

A unit of measurement for an atom, where one AMU is equal to the mass of one proton; there are $6 \times 10^{23}$ AMUs in one gram.

Valence Electrons

The electrons in the outermost energy level of an atom that are transferred or shared when atoms bond together.

Metals

Elements characterized as being shiny, good conductors of heat and electricity, ductile, and malleable.

Ductile

A property of metals that allows them to be stretched into thin wires.

Malleable

A property of metals that allows them to be pounded into thin sheets.

Non-Metals

Elements that are poor conductors of heat and electricity, are not ductile or malleable, and are often brittle or gaseous.

Metalloids

Elements with properties of both metals and non-metals that conduct heat and electricity better than non-metals but not as well as metals.

Family (or Group)

A vertical column of elements in the periodic table that share similar chemical properties and the same number of valence electrons.

Period

A horizontal row of elements in the periodic table whose properties change greatly across the row.

Alkali Metals

The highly reactive elements in the first column of the periodic table (Group 1) that have one valence electron and are never found free in nature.

Rule of Octet

The principle that all atoms (except hydrogen) want to have 8 electrons in their outermost energy level to be stable.

Alkaline Earth Metals

Group 2 elements that have two valence electrons and are never found uncombined in nature.

Transition Metals

The elements in the B families (Groups 3–12) that are good conductors and often form brightly colored compounds.

Boron Family

The periodic group that includes boron and aluminum; aluminum is the most abundant metal in the Earth's crust.

Carbon Family

The family of elements with four valence electrons, including carbon, which is known as the "basis of life."

Nitrogen Family

The family named after the element that makes up $78\%$ of the Earth's atmosphere; these atoms have 5 valence electrons.

Oxygen Family

The family of elements with 6 valence electrons; oxygen is the most abundant element in the Earth's crust.

Halogen Family

The most active non-metals, which have 7 valence electrons and react with alkali metals to form salts.

Noble Gases

Colorless, extremely un-reactive (inert) gases whose outermost energy levels are full.

Rare Earth Elements

The thirty elements composed of the lanthanide and actinide series, many of which are synthetic or man-made.

Compound

A pure substance made of two or more elements chemically combined that can be broken down into simpler substances.

Molecule

The smallest unit of a compound, consisting of two or more atoms chemically bonded together.

Subscript

Small numbers placed to the lower right of chemical symbols representing the number of atoms of an element in a compound.

Law of Conservation of Mass

The scientific law stating that in a chemical equation, the left side must have the same number of atoms of each element as the right side.

Coefficient

The large number in a chemical formula that indicates how many molecules of the substance are present.

Corrosion

A chemical property of metals involving a reaction with water.