BIO 111 Chapter 2 Key Terms

atom

the smallest unit of matter that retains all of the chemical properties of an element

nucleus

core of an atom; contains protons and neutrons

proton

positively charged particle that resides in the atom’s nucleus; has a mass of one amu and a charge of +1

electron

negatively charged subatomic particle that resides outside of the nucleus in the electron orbital; lacks functional mass and has a negative charge of -1 unit

neutron

uncharged particle that resides in an atom’s nucleus; has a mass of one amu

ion

atom or chemical group that does not contain equal numbers of protons and electrons

energy level/shell

fixed area at a certain distance around an atom’s center where electrons are found, shells closest lowest energy, shells farthest most energy

periodic table

organizational chart of elements indicating each element’s atomic number and atomic mass; provides key information about the elements’ properties

valence electrons

electrons on the outermost shell of an atom (valence shell)

covalent bond

type of strong bond formed between two atoms of the same or different elements; forms when electrons are shared between atoms

polar vs nonpolar

polar: forms as a result of unequal electron sharing, slightly positive and negative charged molecule regions, nonpolar: forms between atoms when electrons are shared equally between them

ionic bond

chemical bond that forms between ions with opposite charges (cations and anions)

electronegativity

ability of some elements to attract electrons (often of hydrogen atoms), acquiring partial negative charges in molecules and creating partial positive charges on the hydrogen atoms

hydrophilic

describes ions or polar molecules that interact well with other polar molecules such as water

hydrophobic

describes uncharged nonpolar molecules that do not interact well with polar molecules such as water

hydrogen bond

weak bond between slightly positively charged hydrogen atoms and slightly negatively charged atoms in other molecules

tricylglycerol

a type of lipid molecule formed from one glycerol backbone and three fatty acids

saturated

fatty acid chain has only single covalent bonds and holds the maximum number of hydrogen atoms

unsaturated

fatty acid chain has one or more carbon-carbon double bonds

van der Waals interactions

very weak interaction between molecules due to temporary changes attracting atoms that are very close together