AP Biology Chapter 2: The Chemical Context of Life

94977315	Matter	anything that takes up space and has mass
94977316	Element	any substance that cannot be broken down into simpler substances
94977317	Compound	a substance that contains two or more elements chemically combined in a fixed ratio
94977318	Trace Elements	those required by an organism in only minute quantities
94977319	Atom	smallest unit of matter that still retains the properties of an element
94977320	Neutrons	the particles of the nucleus that have no charge
94977321	Protons	positively charged particles in the nucleus of an atom
94977322	Electrons	These have a negative charge and orbit the nucleus
94977323	Atomic Nucleus	the center of an atom
94977324	Dalton	unit of measurement used for atoms and subatomic particles
94977325	Atomic Number	the number of protons in the nucleus of an atom
94977326	Mass Number	the sum of the number of neutrons and protons in an atomic nucleus
94977327	Atomic Mass	An approximation of the total mass of an atom
94977328	Isotopes	atoms of the same element that have different numbers of neutrons
94977329	Radioactive Isotope	An isotope whose nucleus decays spontaneously, giving off particles and energy.
94977330	Energy	capacity to cause change
94977331	Potential Energy	energy that matter possesses because of its location or structure
94977332	Energy Levels	The different states of potential energy that electrons have in an atom
94977333	Electron Shells	an energy level representing the distance of an electron from the nucleus of an atom.
94977334	Valence Electrons	electrons on the outermost energy level of an atom
94977335	Valence Shell	outermost electron shell
94977336	Orbital	a region of space around the nucleus where an electron is likely to be found
94977337	Covalent Bond	a chemical bond that involves sharing a pair of electrons between atoms in a molecule
94977338	Chemical Bond	the force that holds two atoms together
94977339	Molecule	two or more atoms held together by covalent bonds
94977340	Single Bond	a covalent bond in which two atoms share one pair of electrons.
94977341	Structural Formula	an expanded molecular formula showing the arrangement of atoms within the molecule
94977342	Molecular Formula	a chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms.
94977343	Double Bond	a covalent bond in which two pairs of electrons are shared between two atoms
94977344	Valence	the bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atom's outermost (valence) shell.
94977345	Electronegativity	the attraction of an atom for the electrons of a covalent bond
94977346	Non polar covalent bond	bond where electrons are shared equally
94977347	polar covalent bond	a covalent bond in which electrons are not shared equally
94977348	Ion	a charged atom
94977349	Anion	a negatively charged ion
94977350	Cation	a positively charged ion
94977351	Ionic Bond	a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains to electron to form a negative ion
94977352	Ionic Compound	Compound formed of ionic bonds
94977353	Hydrogen Bond	A type of weak chemical bond formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule.
94977354	Van der Waals interactions	weak attractions that occur only when atoms and molecules are very close together
94977355	Reactants	the starting materials in a chemical reaction
94977356	Products	Ending materials in a chemical reaction.
94977357	Chemical Equilibrium	in a reversible chemical reaction, the point at which the rate of the forward reaction equals the rate of the reverse reaction.