LESSON 1: Atoms, Molecules and Ions

Metalloids

are chemical elements that have properties intermediate between those of metals and nonmetals, also called semimetals

Nonmetals

are chemical elements that lack typical metallic characteristics, such as being dull, brittle (if solid), and poor conductors of heat and electricity

Noble Gases

are elements in Group 18 of the periodic table that are characterized by their full valence electron shells, making them chemically inert and unreactive under normal conditions

Halogens

group VIIA (17) of the periodic table ; they are reactive non-metallic elements that form strongly acidic compounds with hydrogen from which simple salts can be made

Metals

are a majority group of elements on the periodic table, found mainly on the left and in the center, characterized by properties such as shininess, hardness, high density, good conductivity of heat and electricity, and malleability and ductility

Atom

smallest unit of matter that retains the identity and properties of an element ; protons and electrons are balanced

Molecule

a group of two or more atoms that are chemically bonded

Nucleons

Proton + Neutron =

Proton

a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron ; located in the nucleus ; the identity of the element

Neutron

a subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen ; located in the nucleus

Electron

a stable subatomic particle with a charge of negative electricity, found in all atoms and acting as the primary carrier of electricity in solids ; located in the shell

Neutral Atom

is an atom with no overall electric charge, meaning it possesses an equal number of positively charged protons and negatively charged electrons

Mass Number

is the sum of protons and neutrons in an atom's nucleus, but it's not the number listed on the periodic table

Atomic Number

represents the number of protons in an atom's nucleus, which uniquely identifies an element

International Union of Pure and Applied Chemistry

agrees on compounds, symbols, etc

Ion

is formed when an atom gains or loses electron

Cation

positively charged, formed when a metal loses electron

Anion

negatively charged, formed when a nonmetal gains electron

Isotopes

atoms of the same element but with different mass numbers

Monatomic Ions

an entity, such as a gas or molecule, that consists of a single atom and is not bound to other atoms

Stock System

uses a Roman numeral in parentheses after the element's name to indicate the specific positive charge of the ion

Classical System

applies specifically to transition metals that form multiple positive charges, using the suffixes -ous for the lower charge and -ic for the higher charge appended to the element's Latin-derived stem

Ionic Compound

a neutral chemical substance composed of cations and anions held together by electrostatic attraction in a process called an ionic bond

Polyatomic Ions

containing multiple atoms, usually more than two, held together as a single unit

Covalent Compounds

a substance formed when two or more nonmetal atoms share valence electrons to form covalent bonds, creating a discrete molecule

Hydrated Salts

some ionic compounds with water molecules incorporated in their structure

Anhydrous

no water molecules ; when heated, no water

Acids

are compounds that can give off hydrogen ions when dissolved in water (aqueous)

Arrhenius acid

substance that yields H+ in aqueous solution

Binary Acid

an acid that contains only two different elements: hydrogen and a single nonmetal, typically a halogen (fluorine, chlorine, bromine, iodine, astatine) or sulfur

Ternary Acid

an acid that forms from a polyatomic ion ; the suffix -ite is replaced with -ous, and the -ate with -ite

Relative Atomic Mass

the weighted average mass of the isotope of an element compared to 1/12 of the mass of a carbon-12 atom

Carbon-12

the most abundant isotope ; used as the standard reference for measuring relative atomic mass

Average Atomic Mass

the weighted average of the masses of an element's isotopes, taking into account their natural abundance, and is found on the periodic table

Formula Mass

is a term used for the sum of the atomic mass of constituents atoms

Molecular Mass

is a term for the average relative mass of a single molecule