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Bio: Chapter 2

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matter
anything that takes up space and mass
element
substance that cannot be broken down to other substances by chemical reaction
compound
substance consisting of two or more different elements combined in a fixed ratio
trace elements
an element indispensable for life but required in extremely minimum amounts
atom
The smallest unit of matter that still retains the properties of an element
neutrons
the particles of the nucleus that have no charge
protons
positively charged particles in the nucleus of an atom
electrons
negatively charged particles found outside the nucleus
atomic nucleus
atom's dense central core, containing protons and neutrons
dalton
measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu
atomic number
the number of protons in the nucleus of an atom
mass number
the sum of the number of neutrons and protons in an atomic nucleus
atomic mass
total mass of an atom, which is the mass in grams of 1 mole of the atom
isotopes
atoms of the same element that have different numbers of neutrons
radioactive isotope
isotope that is unstable; nucleus decays spontaneously, giving off detectable partices and energy
energy
capacity to cause change, especially to do work (move matter against an opposing force)
potential energy
emergy that matter possesses as a result of its location or spatial arrangement (structure)
electron shells
energy level of electrons at a characteristic avg. distance from nucleus of atom
valence electrons
The electrons in the outermost shell (main energy level) of an atom; these are the electrons involved in forming bonds.
valence shell
The outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.
orbital
3 dimensional space where an electron is found 90% of the time
chemical bonds
an attraction between two atoms resulting from the sharing of outer-shell electrons or the presence of opposite charges
molecule
two or more atoms held together by covalent bonds
single bond
a single covalent bond; the sharing of a pair of valence electrons by two atoms.
structural formula
A type of molecular notation in which the constituent atoms are joined by lines representing covalent bonds.
molecular formula
a type of molecular notation representing the quantity of constituent atoms, but not the nature of the bonds that join them.
double bond
a double covalent bond; the sharing of two pairs of valence electrons by two atoms.
valence
the bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atom's outermost (valence) shell.
electronegativity
The attraction of a given atom for the electrons of a covalent bond.
nonpolar covalent bond
A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
polar covalent bond
A covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.
ion
an atom orgroup of atoms that has gained or lost one more electrons; thus acquiring a charge
cation
a positively charged ion
anion
a negatively charged ion
ionic bond
a chemical bond resulting from the attraction between oppositely charged ions.
ionic compounds or salts
A compound resulting from the formation of an ionic bond.
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.
van der Waals interactions
Weak attractions between molecules or parts of molecules that are brought about by localized charge fluctuations.
chemical equilibrium
in a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time.
covalent bond
sharing of a pair of valence electrons by two atoms.
chemical reactions
The making and breaking of chemical bonds, leading to changes in the composition of matter.
reactants
the starting materials in a chemical reaction
products
Ending materials in a chemical reaction.