Biology unit 6

Dfran 9th grade biology unit 6

proton charge

positive

electron charge

negative

neutron charge

neutral

atom

building blocks of matter

nucleus

the center of an atom where protons and neutrons are located

energy levles

areas outside of the nucleus occupied by electrons

valence electrons

outermost electrons that determine the reactivity of an atom

element

a pure substance that cannot be broken down

atomic number

the number of protons in the nucleus of an atom

mass number

the number of protons and neutrons

atomic weight

average amount of neutrons in an element

period

horizontal rows on the periodic table

group

vertical columns on the periodic table

isotope

atoms of the same element that have the same number of protons and electrons but have a different number of neutrons

radioactive isotope

isotopes that give off radiation

compound

a pure substance formed when two or more different elements combine

covalent bond

the chemical bond that forms when electrons are shared

molecule

a compound in which the atoms are held together by covalent bonds

ion

an atom that has lost or gained one or more electrons

ionic bond

an electrical attraction between two oppositely charged atoms

van der Waals forces

attractions between molecules

chemical reaction

the process by which atoms or groups of atoms in substances are recognized into different substances

reactant

starting substances to the left of the arrow

product

formed substances to the right of the arrow

Activation energy

the minimum amount of energy needed for reactants to form products

catalyst

substances that lowers the activation energy needed to start a chemical reaction

enzyme

a substance produced by a living organism which acts as a catalyst

polar molecules

molecules that have an uneven distribution of charge

hydrogen bond

a weak interaction involving hydrogen atoms and a fluorine, oxygen, or nitrogen atom

mixture

combination with two or more substances that don’t create a chemical reaction

homogeneous mixture

a uniform mixture

solvent

able to dissolve other substances (water)

solute

substance that dissolves

heterogeneous mixture

a mixture with distinctive substances

suspension

a type of heterogeneous mixture where the particles settle out overtime

acid

substance that releases H+ ions when they dissolve

base

substance that releases OH- ions when they dissolve

pH

the measure of concentration of H+ in a solution

macromolecules

large molecules that are formed by joining smaller organic molecules together

polymer

molecules made from repeating units of identical or nearly identical compounds called monomers

carbohydrate

compounds composed of a ratio of 1 carbon :2 hydrogen :1 oxygen

lipid

molecules made mostly of carbon and hydrogen that make up the fats, oils, and waxes

proteins

compounds made of smaller carbon compounds called amino acids

nucleic acids

complex macromolecules that transmit and store genetic information