Anatomy & Physiology - Chapter 2 Questions with Correct Answers

elements - substance composed of only one type of atom that cannot be broken into simpler constituents by chemical means compounds - chemical combination of two or more elements atoms - smallest particle of a chemical element that retains the properties of that element; particles that combine to form molecules subatomic particles - particles that make up atoms; neutrons, protons, electrons nucleus - dense, central core of an atom protons - positively charged subatomic particle neutrons - neutral subatomic particle electrons - small, negatively charged subatomic particle atomic number - number of protons in an atom of an element mass number (atomic mass) - number of protons plus the number of neutrons in an atom of an element energy level - limited region surrounding the nucleus of an atom at a certain distance containing electrons; shell octet rule - atoms with fewer or more than eight electrons in the outer energy level will attempt to lose, gain, or share electrons with other atoms to achieve stability inert - stable element; maximum amount of electrons in outer shell atomic weight - average atomic mass of an atom of an element as it is found in nature; atomic weights are usually found in the periodic table of elements radioisotope - unstable isotope that undergoes nuclear breakdown and emits nuclear particles and radiation decay - emition of nuclear particles and radiation chemical reaction - interaction between two or more atoms that occurs as a result of activity between electrons in their outermost energy levels molecules - two or more atoms covalently joined together chemical bonds - energy relationship joining two or more atoms; involves sharing or exchange of electrons ions - electrically charged atom or group of atoms ionic bond (electrovalent bond) - formed by transfer of electrons; strong electrostatic force that binds positively and negatively charged ions together covalent bond - formed by sharing of electron pairs between atoms single covalent bond - covalent bond with only one pair of shared electrons double covalent bond - covalent bond with two pairs of shared electrons