Download Chemistry Terms

Chemistry Terms
atomic number The atomic number of an element is the number of protons in the nucleus of each atom.
chemical reaction A process in which atoms and molecules interact, resulting in the alteration of their
molecular structures.
covalent bond An atomic bond in which an electron is a resident of the outer electron shell of both
atoms involved in the bond.
electric charge The property that a particle must have in order to feel the electromagnetic force. It can
be positive or negative.
electromagnetic (EM) force The fundamental force of nature that a particle feels if it has electric charge.
electron By far the lightest of the 3 particles that make up atoms. They orbit the nucleus and have an
electric charge of -1.6 × 10-19 Coulombs.
electron shell A spherical region centered on the nucleus of an atom in which an electron resides. From
the inside out, the orbitals hold respectively 2, 8, 8, 18, 18, 32 electrons.
element All atoms with the same number of protons in their nuclei are said to be atoms of the same
element.
endothermic (reaction) A chemical reaction that requires an input of energy to drive it.
exothermic (reaction) A chemical reaction in which energy is released to the environment.
ionic bond A bond between atoms in which an electron from one atom leaves and resides in the other
shell of the other atom, giving both atoms a net electric charge such that they attract each other and
stick together.
metallic bond The kind of bond holding atoms together in metals. The bonding electrons are not
residents of the outer shells of any atoms, but are free to move amongst the atoms.
neutron One of the two types of particles that make up an atomic nucleus. Its electric charge is zero.
non-metal Elements that do not exibit metallic properties. They occupy the upper right portion of the
periodic table of elements.
periodic table of elements A gridlike listing of the known elements that is arranged such that elements
within vertical row have similar properties.
proton One of the two types of particles that make up an atomic nucleus. It has an electric charge of
+1.6 × 10-19 Coulombs.
valence shell The outer electron shell of an atom.
Nuclear Physics Terms
daughter isotope The isotope into which a radioisotope transforms. A radioisotope can have several
possible daughter isotopes, depending on the process by which it decays.
halflife The amount of time necessary for half a sample of a radioisotope to decay to its daughter
isotope. This is different for each radioisotope.
isotope Each nucleus has some number of protons and neutrons. A particular number combination is an
isotope.
radioactive decay The transformation of an unstable nucleus into another nucleus (or nuclei).
radioisotope An isotope that is unstable (it will eventually decay to another isotope).
strong nuclear force The force that holds together atomic nuclei. It's attractive between protons,
between neutrons, and between a proton and neutron.
Electricity Terms
AC & DC Alternating Current and Direct Current. DC is electricity moving in one direction (batteries
produce this). AC is current moving back and forth (this is how it comes out of electrical receptacles).
Ampere see electric current
Coulomb The standard international unit of electric charge. It's the amount of charge on about 6.2415
quintillion protons.
electric circuit A closed loop around which electric current can flow.
electric current The flow of electric charge. When charged particles move (usually when electrons flow
through matter) they carry charge. Metric unit is the Ampere, which is one Coulomb per Second.
electrostatic force The attractive or repulsive force between 2 charged particles. The particles
experience this force regardless of their motion.
energy A dynamic quantity in physics responsible for motion.
kinetic energy The energy of motion. When an object with mass m is moving at speed v its kinetic
energy is KE = ½mv².
Joule The metric unit of energy. It's the amount of energy required to lift 1 kilogram (2.2 pounds) about
10 centimeters (about 4 inches).
magnetic field The magnetic force field produced by moving charges that affects other moving charges.
One can compute the total field due to many moving charges and thus simplify the computation of force
on another moving charged particle.
magnetism The second componant of the electromagnetic force. Two particles only interact through
this force only when they are both moving. The magnitude of the force depends on the speeds of the 2
particles and the direction of the force depends on the directions that both are moving.
potential energy Energy that's stored in some form. Examples are chemical potential energy,
gravitational, nuclear, & spring energy.
power Rate of energy flow. Metric unit is the Watt, equal to one Joule per Second.
voltage Electric potential, energy per charge. In a 120 volt wall socket, each Coulomb of electron charge
carrys 120 Joules of energy. Metric unit is the Volt, which is one Joule per Coulomb.
Watt see power