Classification of Matter & Chemical Formulas

Vocabulary flashcards covering key terms related to the classification of matter, chemical formulas, and ionic versus covalent compounds.

Pure Substance

Matter that has a fixed composition and distinct properties.

Mixture

A physical combination of substances that can be separated; composition may vary.

Element

A pure substance composed of only one type of atom.

Compound

A substance made of two or more different atoms chemically bonded together.

Homogeneous Mixture

A mixture with a uniform composition throughout (also called a solution).

Heterogeneous Mixture

A mixture with non-uniform composition where components are visibly distinct.

Chemical Formula

An expression that shows the elements in a compound and the relative number of each atom.

Subscript (in formulas)

The small number written after an element symbol indicating how many atoms of that element are present.

Coefficient (in equations)

The number placed in front of a formula that multiplies the entire compound or element.

Ionic Compound

A compound composed of cations and anions (generally a metal with a non-metal) held together by ionic bonds.

Covalent Compound

A compound composed mainly of non-metals that share electrons in covalent bonds.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Binary Ionic Compound

An ionic compound that contains monoatomic ions of two different elements (e.g., NaCl).

Criss-Cross Method

A technique for writing ionic formulas by crossing the magnitude of each ion’s charge to become the other’s subscript, then reducing if necessary.

Transition Metal

A metal element whose ionic charges can vary (charge must often be specified with Roman numerals).

Monoatomic Ion

A single atom that has gained or lost electrons to acquire a charge.

Polyatomic Ion

A charged group of covalently bonded atoms that acts as a single ion in compounds.

Ammonium

NH₄⁺, a common polyatomic cation with a +1 charge.

Hydroxide

OH⁻, a common polyatomic anion with a –1 charge.

Acetate

C₂H₃O₂⁻, a polyatomic anion with a –1 charge.

Permanganate

MnO₄⁻, a polyatomic anion with a –1 charge.

Nitrate

NO₃⁻, a polyatomic anion with a –1 charge.

Bicarbonate

HCO₃⁻, a polyatomic anion with a –1 charge.

Carbonate

CO₃²⁻, a polyatomic anion with a –2 charge.

Sulfate

SO₄²⁻, a polyatomic anion with a –2 charge.

Phosphate

PO₄³⁻, a polyatomic anion with a –3 charge.