Atoms and Elements Vocabulary

A set of vocabulary flashcards covering key terms and definitions related to atoms and elements.

Atomic Mass

The total mass of an atom, mostly determined by the number of protons and neutrons, measured in atomic mass units (amu).

Subscript

A small number written at the lower right of a chemical symbol, showing how many atoms of that element are in a molecule.

Alkali Metals

A group of very reactive metals with 1 valence electron, making them react easily with other elements.

Alkaline Earth Metals

Elements in Group 2 of the Periodic Table, with 2 valence electrons; reactive but less so than alkali metals.

Chemical Formula

Uses symbols and numbers to show the types and numbers of atoms in a substance.

Atom

The smallest unit of matter that retains the properties of an element.

Post Transition Metals

Elements found just to the right of transition metals on the Periodic Table, generally in Groups 13–16.

Periodic Table

An organized chart of all known elements, arranged by atomic number and grouped by similar chemical properties.

Noble Gases

Elements in Group 18 of the Periodic Table, very stable and unreactive with a full set of valence electrons.

Ball & Stick

A 3D representation of a molecule showing atoms as balls and bonds as sticks.

Metalloids

Elements that have properties of both metals and nonmetals; often called semiconductors.

Electrons

Negatively charged subatomic particles found outside the nucleus of an atom.

Nonmetals

Elements that generally lack the properties of metals, often poor conductors, dull, and brittle.

Chemical Equation

A written representation of a chemical reaction, e.g., H₂ + O → H₂O.

Element

A pure substance made of only one type of atom.

Atomic Number

The number of protons in the nucleus of an atom.

Proton

A positively charged subatomic particle found in the nucleus of an atom.

Coefficient

A number placed in front of a chemical formula indicating how many molecules or atoms are involved in a reaction.

Molecule

A group of two or more atoms that are chemically bonded together.

Compound

A substance made of two or more different elements that are chemically bonded together in a fixed ratio.

Periods

Horizontal rows of elements in the Periodic Table with similar number of electron shells.

Neutron

A neutral subatomic particle found in the nucleus of an atom, adding mass to the atom.

Halogens

Elements in Group 17 of the Periodic Table, very reactive nonmetals with 7 valence electrons.

Groups

Vertical columns of elements in the Periodic Table with similar chemical properties.

Lanthanides

A group of rare earth metals found in the Periodic Table, usually shown in a separate row at the bottom.

Ion

An atom or molecule that has gained or lost electrons, resulting in a positive or negative charge.

Lewis Structure

A diagram that shows the valence electrons of atoms in a molecule using dots and lines.

Chemical Symbol

A one- or two-letter abbreviation that represents a chemical element.

Transition Metals

Elements in the middle section of the Periodic Table, known for high strength and good conductivity.