Knowt 2 - Atoms, Molecules, & Ions

Dalton’s Atomic Theory

Matter consists of indivisible atoms that combine in fixed ratios during chemical changes

Law of constant composition

All samples of a pure compound contain the same elements in the same proportions by mass

Law of definite proportions

All samples of a pure compound contain the same elements in the same proportions by mass

Law of multiple proportions

When two elements form multiple compounds, a fixed mass of one element reacts with masses of the other in small whole-number ratios

Electron

Negatively charged subatomic particle located outside the nucleus

Fundamental unit of charge

The magnitude of an electron's charge, equal to 1.602 × 10⁻¹⁹ C

Proton

Positively charged subatomic particle in the nucleus

Neutron

Uncharged subatomic particle in the nucleus

Isotopes

Atoms of the same element with different numbers of neutrons

Atomic mass

Average mass of atoms of an element in atomic mass units

Atomic mass unit (amu)

Unit of mass equal to 1/12 the mass of a carbon-12 atom

Atomic number (Z)

Number of protons in an atom's nucleus

Mass number (A)

Sum of protons and neutrons in an atom's nucleus

Chemical symbol

One-, two-, or three-letter abbreviation for an element or its atoms

Molecular formula

Formula showing the actual number of atoms of each element in a molecule

Empirical formula

Formula showing the simplest whole-number ratio of atoms in a compound

Structural formula

Formula showing the atoms and their connections in a molecule

Periodic table

Table arranging elements by increasing atomic number with similar properties in columns and rows

Periodic law

Element properties are periodic functions of their atomic numbers

Group

Vertical column in the periodic table

Period (Series)

Horizontal row in the periodic table

Metal

Shiny, malleable element that conducts heat and electricity well

Nonmetal

Dull element that poorly conducts heat and electricity

Metalloid

Element that moderately conducts heat and electricity with properties of both metals and nonmetals

Main-group element (Representative)

Element in groups 1, 2, and 13–18

Transition metal

Element in groups 3–12

Inner transition metal

Element in the bottom two rows, including lanthanides and actinides

Alkali metal

Element in group 1

Alkaline earth metal

Element in group 2

Halogen

Element in group 17

Noble gas

Element in group 18

Ion

Electrically charged atom or molecule with unequal protons and electrons

Cation

Positively charged ion with more protons than electrons

Anion

Negatively charged ion with more electrons than protons

Monatomic ion

Ion consisting of a single atom

Polyatomic ion

Ion consisting of more than one atom

Ionic bond

Electrostatic attraction between oppositely charged ions

Ionic compound

Compound of cations and anions in neutral ratios

Covalent bond

Attractive force from shared electrons between atoms

Covalent compound

Compound of molecules with atoms bonded by shared electrons

Molecular compound

Compound of molecules with atoms bonded by shared electrons

Nomenclature

System of rules for naming compounds

Binary acid

Acid containing hydrogen and one other element, releasing H⁺ ions in water

Hydrate

Compound with water molecules bound in its crystals

Average Mass Equation

Average Mass = ∑_i (fractional abundance x Isotopic mass)_i

Mass Number Equation

A = #protons(+) + #neutrons(o)