Ch 2 Terms

Law of definite proportions/law of constant composition

Joseph Proust, all samples of a pure substance contain the same elements in the same proportions according to the mass ratio of the elements in the compound

law of multiple proportions

John Dalton, when two elements combine to form more than one compound, the traits of the ratios of their masses will be small whole numbers

1 amu = _____ the mass of carbon atom

1/12

atomic charge

number of protons - number of electrons

cations

positively charge ion

anion

negatively charged ion

isotopes

elements that have the same atomic number but different atomic masses

atomic mass

approximately equal to the sum of protons and neutrons in the nucleus

molecule

two or more atoms (same or different) joined together by forces or bonds

empirical formula

shows the types of atoms in the molecule and gives the number of each atom involved in the simplest whole number ratio; formula is empirical if subscripts cannot be divided by a common number

molecular formula

shows the actual number of atoms in the molecule; molecular formula may be the same as the empirical formula; always a whole number multiple of the empirical formula

isomers

molecules that have the same types of numbers of atoms but differ in the way the atoms are connected to each other

structural isomers (constitutional)

differ in the way the atoms are connected

spacial isomers (stereoisomers)

connectivity is the same but spatial orientation, 3D arrangement is different

metals

shiny, malleable, ductile, good conductors of heat and electricity; located to the left of the stair-step line

nonmetals

dull, poor conductors of heat and electricity; located to the right of the stair-step line

metalloids

moderate conductors of heat and electricity; have properties of metals and nonmetals; located on either side of the stair-step line (directly touching); this excludes aluminum which is a metal

ionic bond

bond formed between a cation (+) and an anion (-); electrostatic forces hold the atoms together

covalent bond

bond formed when two atoms share one or more pairs of electrons

ionic compound

contains ionic bonds; involves a metal and one or more nonmetals

molecular compound

contains covalent bonds; involves two or more nonmetals