Chem Review terms Flashcards
anything that takes up space and has mass
Matter
is a pure substance that is distinguished from all other matter by the fact that it cannot be created or broken down by ordinary chemical means
Element
is a substance composed of two or more elements joined by chemical bonds.
Compound
smallest quantity of an element that retains the unique properties of that element
“are the smallest stable units of matter”
Atom
Atoms are composed of _____ that determine the structure of an object
subatomic particles
the number of protons in the nucleus of the atom, identifies the element.
Atomic Number
is the sum of the number of protons and neutrons in its nucleus
mass number
is one of the different forms of an element, distinguished from one another by different numbers of neutrons. (elements whose atoms nuclei contain the same number of protons but a different number of neutrons)
isotrope
•an isotope whose nucleus readily decays, giving off subatomic particles and electromagnetic energy
radioactive isotope
is a layer of electrons that encircle the nucleus at a distinct energy level.
electron shell
•is an atom’s outermost electron shell
valence shell
•All atoms (except hydrogen and helium with their single electron shells) are most stable when there are exactly eight
octet rule
the average of the mass of all its isotopes
Atomic mass (or weight
(= electron shell model) – depicts electrons in circular orbitals or shells around the nucleus
Planetary model
(= electron cloud model) – depicts “probable” regions of greatest electron density by shading
Orbital model
a weak or strong electrical attraction that holds atoms in the same vicinity
bond
A more or less stable grouping of two or more atoms held together by chemical bonds
molecule
When a molecule is made up of two or more atoms of different elements
chemical compound
An atom that has an electrical charge—whether positive or negative
ion
A positively charged ion
cation
A negatively charged ion
anion
an ongoing, close association between ions of opposite charge
ionic bond
meaning chemically unreactive element due to already having a full valence shell
inert
molecules share electrons in a mutually stabilizing relationship.
covalent bond
e-’s shared equally between atoms in covalent bond
Nonpolar Covalent Bonds
e-’s not shared equally between atoms in covalent bond
Polar Covalent Bonds
is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for
example, the oxygen in the water molecule) is attracted to another electronegative atom from another molecule
hydrogen bond
is the form of energy powering any type of matter in motion
kinetic energy
the form of potential energy in which energy is stored in chemical bonds
chemical energy
is the energy of position, or the energy matter possesses because of the positioning or structure of its components.
potential energy
Chemical reactions that release more energy than they absorb are
exergonic
chemical reactions that absorb more energy than they release are
endergonic
is energy stored in physical systems such as machines, engines, or the human body, directly powers the movement of matter.
mechanical energy
is energy emitted and transmitted as waves rather than matter
radiant energy
supplied by electrolytes in cells and body fluids, contributes to the voltage changes that help transmit impulses in nerve and muscle cells
electrical energy
one or more substances that enter into the reaction.
reactant
one or more substances produced by a chemical reaction
product
is a chemical reaction that results in the joining of components that were formerly separate
synthesis reaction
is a chemical reaction that breaks down something larger into its constituent parts
decomposition reaction
is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both
formed and broken, and chemical energy is absorbed, stored, and released
exchange reaction
the capacity to do work
energy
is a substance that increases the rate of a chemical reaction without itself undergoing any change
catalyst
is a catalyst composed of protein or ribonucleic
acid (RNA)
enzyme
the “threshold” level of
energy needed to break the bonds in the reactants
activation energy
decomposition reactions which produce ATP from food molecules
- are also a type of exchange reaction as electrons are transferred between atoms and molecules
Oxidation-reduction reactions