Atomic Mass, Isotopes, and Matter

Vocabulary flashcards covering key terms from the lecture notes on matter, isotopes, atomic mass, ions, and polyatomic ions.

Matter

Anything that has mass and occupies space.

Mass

A measure of the amount of matter in an object.

States of Matter

Forms of matter: solid, liquid, and gas.

Solid

State with fixed shape and fixed volume.

Liquid

State with fixed volume but variable shape.

Gas

State with variable shape and volume.

Pure Substance

Matter with fixed composition throughout.

Element

A substance consisting of a single type of atom.

Compound

A substance formed when two or more elements are chemically joined.

Mixture

A substance with variable composition made of two or more components.

Homogeneous

Uniform composition throughout.

Heterogeneous

Non-uniform composition.

Distilled Water

Pure substance; water that has been purified by distillation.

Aluminum Foil

Pure substance; elemental aluminum in foil form.

Soil

Mixture; non-uniform composition.

Blood

Mixture; non-uniform composition.

Brass

An alloy; a homogeneous mixture of copper and zinc.

Gold Jewelry

Elemental gold; example of an element.

Helium Balloon

Elemental helium gas used to fill balloons.

Table Sugar

Compound; sucrose (C12H22O11).

Carbon Dioxide

Compound; CO2.

Isotopes

Atoms of the same element with different numbers of neutrons.

Atomic Number

Number of protons in the nucleus; identifies the element.

Mass Number

Total number of protons and neutrons in an atom.

Isotope Notation

Standard notation: A X or X-A, where A is the mass number.

Protium

Hydrogen-1; 1 proton, 0 neutrons.

Deuterium

Hydrogen-2 (³/₂H or D); 1 proton, 1 neutron.

Tritium

Hydrogen-3 (³H or T); 1 proton, 2 neutrons.

Natural Abundance

Percentage of each isotope found in nature.

Chlorine-35

Chlorine isotope with mass 35; ~75.77% natural abundance.

Chlorine-37

Chlorine isotope with mass 37; ~24.23% natural abundance.

Atomic Mass

Weighted average mass of all naturally occurring isotopes of an element.

Atomic Mass Unit (amu)

Unit of mass used for atomic/molar masses; 1 amu defined by carbon-12.

Reference: Carbon-12

Carbon-12 is exactly 12 amu, used as the standard.

Weighted Average Formula

Atomic mass = sum(isotope mass × fractional abundance).

Molar Mass

Mass of 1 mole of a substance (g/mol); 1 amu ≈ 1 g/mol.

1 amu = 1 g/mol

Relation between atomic mass and molar mass.

Ion

An atom or molecule that has gained or lost electrons, giving a net charge.

Cation

Positively charged ion; formed by loss of electrons (e.g., Na⁺).

Anion

Negatively charged ion; formed by gain of electrons (e.g., Cl⁻).

Monatomic Ions

Ions formed from a single element (e.g., Na⁺, Cl⁻).

Polyatomic Ions

Ions made of a group of atoms with an overall charge (e.g., SO₄²⁻, NO₃⁻, NH₄⁺, PO₄³⁻, CO₃²⁻).

Sulfate

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

Nitrate

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

Ammonium

NH₄⁺; a polyatomic cation with a +1 charge.

Phosphate

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

Carbonate

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

Iron(III) Ion

Fe³⁺; iron ion with oxidation state +3.

Oxidation State

Charge number for ions; transition metals are shown with Roman numerals.

Roman Numerals in Ions

Used to denote oxidation states of transition metals (e.g., Fe²⁺ = iron(II) ion).

-ide Ending

For anions, change the element name ending to -ide (e.g., chlorine → chloride).

-ite vs -ate

Suffixes for oxyanions; -ite has one fewer oxygen than -ate (sulfite vs sulfate).

Formula Unit

The lowest whole-number ratio of ions in an ionic compound (e.g., Ca₃(PO₄)₂).