final gen chem terms

absorption spectrum

the spectrum produced when atoms absorb specific wavelengths

amplitude

the height of the crest of a wave; related to the intensity or brightness of the light

angular momentum quantum number (l)

a integer form 0 to n-1, related to the shape of an atomic orbital

atomic orbital (wave function)

the wave function of an electron -- qualitatively used to mean the region of space in which there is a high probability of finding an electron.

d orbital

an atomic orbital with l=2

de Broglie wavelength

the wavelength of a moving particle obtained from the de Broglie equation λ = h/mu

diffraction

The phenomenon in which a wave striking the edge of an object bends around it. A wave passing through a slit as wide as its wavelength forms a circular wave.

electromagnetic radiation

Oscillating, perpendicular electric and magnetic fields moving simultaneously through space as waves and manifested as visible light, x-rays, microwaves, radio waves, and so on.

electromagnetic spectrum

The continuum of radiant energy arranged in order of increasing wavelength.

electron cloud depiction

An imaginary representation of an electron's rapidly changing position around the nucleus over time.

electron density diagram

The pictorial representation for a given energy sublevel of the quantity ψ2 (the probability density of the electron lying within a particular tiny volume) as a function of r (distance from the nucleus).

emission spectrum

The line spectrum produced when excited atoms return to lower energy levels and emit photons characteristic of the element.

excited state

Any electron configuration of an atom (or ion or molecule) other than the lowest energy (ground) state.

f orbital

An atomic orbital with l = 3.

flame test

A procedure for identifying the presence of metal ions in which a granule of a compound or a drop of its solution is placed in a flame to observe a characteristic color.

frequency

The number of complete waves, or cycles, that pass a given point per second, expressed in units of 1/second, or s−1 [also called hertz (Hz)]; related inversely to wavelength.

ground state

The electron configuration of an atom (or ion or molecule) that is lowest in energy.

infrared (IR)

The region of the electromagnetic spectrum between the microwave and visible regions.

level (shell)

A specific energy state of an atom given by the principal quantum number n.

line spectrum

A series of separated lines of different colors representing photons whose wavelengths are characteristic of an element.

magnetic quantum number (ml)

An integer from −l through 0 to +l that specifies the orientation of an atomic orbital in the three-dimensional space about the nucleus.

node

A region of an orbital where the probability of finding the electron is zero.

p orbital

An atomic orbital with l = 1.

photoelectric effect

The observation that, when monochromatic light of sufficient frequency shines on a metal, an electric current is produced.

photon

A quantum of electromagnetic radiation.

Planck's Constant

A proportionality constant relating the energy and frequency of a photon, equal to 6.626 × 10−34 J·s.

Principle quantum number (n)

A positive integer that specifies the energy and relative size of an atomic orbital; a number that specifies an energy level in an atom.

probability contour

A shape that defines the volume around an atomic nucleus within which an electron spends a given percentage of its time.

quantum

A packet of energy equal to hν. The smallest quantity of energy that can be emitted or absorbed.

shrondinger equation

An equation that describes how the electron matter-wave changes in space around the nucleus. Solutions of the equation provide energy states associated with the atomic orbitals.

s orbital

An atomic orbital with l = 0.

quantum mechanics

The branch of physics that examines the wave nature of objects on the atomic scale.

quantum number

A number that specifies a property of an orbital or an electron.

radial probability distribution plot

The graphic depiction of the total probability distribution (sum of ψ2) of an electron in the region near the nucleus.

refraction

A phenomenon in which a wave changes its speed and therefore its direction as it passes through a phase boundary into a different medium.

spectrometry

Any instrumental technique that uses a portion of the electromagnetic spectrum to measure the atomic and molecular energy levels of a substance.

speed of light

A fundamental constant giving the speed at which electromagnetic radiation travels in a vacuum: c = 2.99792458 × 108 m/s.

spin quantum number (ms)

A number, either +1/2 or -1/2 that indicates the direction of electron spin.

sublevel (subshell)

An energy substate of an atom within a level. Given by the n and l values, the sublevel designates the size and shape of the atomic orbitals.

ultraviolet (UV)

Radiation in the region of the electromagnetic spectrum between the visible and the x-ray regions.

uncertainty principle

The principle stated by Heisenberg that it is impossible to know simultaneously the exact position and velocity of a particle; the principle becomes important only for particles of very small mass.

wavelength

wave-particle duality

The distance between any point on a wave and the corresponding point on the next wave, that is, the distance a wave travels during one cycle.

stationary state

In the Bohr model, one of the allowable energy levels of the atom in which it does not release or absorb energy.

actinides

The Period 7 elements that constitute the second inner transition series (5f block), which includes thorium (Th; Z = 90) through lawrencium (Lr; Z = 103).

amphoteric

Able to act as either an acid or a base.

atomic size

A measure of how closely one atom lies next to another, determined from the distances between nuclei of adjacent atoms.

aufbau principle

The conceptual approach for building up atoms by adding one proton at a time to the nucleus and one electron to the lowest energy sublevel that is available, to obtain the ground-state electron configurations of the elements

covalent radius

One-half the shortest distance between nuclei of identical covalently bonded atoms.

diamagnetic

A species that is not attracted by a magnetic field because its electrons are paired.

effective nuclear charge (Zeff)

The nuclear charge an electron actually experiences as a result of shielding effects due to the presence of other electrons.

electron affinity (EA)

The energy change (in kJ) accompanying the addition of 1 mol of electrons to 1 mol of gaseous atoms or ions.

electron configuration

The distribution of electrons within the levels and sublevels of the atoms of an element; also the notation for such a distribution.

Hund's rule

A principle stating that, when orbitals of equal energy are available, the electron configuration of lowest energy has the maximum number of unpaired electrons with parallel spins.

inner (core) electrons

Electrons that fill all the energy levels of an atom except the valence level; electrons also present in atoms of the previous noble gas and any completed transition series.

inner transition elements

The elements of the periodic table in which the seven inner f orbitals are being filled; the lanthanides and the actinides.

ionic radius

The size of an ion as measured by the distance between the nuclei of adjacent ions in a crystalline ionic compound.

ionization energy (IE)

The energy (in kJ) required for complete removal of 1 mol of electrons from 1 mol of gaseous atoms or ions

isoelectronic

Having the same number and configuration of electrons as another species.

Lanthanides

The Period 6 (4f) series of inner transition elements, which includes cerium (Ce; Z = 58) through lutetium (Lu; Z = 71).

metallic radius

One-half the shortest distance between the nuclei of adjacent individual atoms in a crystal of an element.

orbital diagram

A depiction of orbital occupancy in terms of electron number and spin shown by means of arrows in a series of small boxes or on a series of short lines

outer electrons

Electrons that occupy the highest energy level (highest n value) and are, on average, farthest from the nucleus

paramagnetic

A species with unpaired electrons that is attracted by an external magnetic field.

Pauli exclusion principle

A principle developed by Wolfgang Pauli stating that no two electrons in an atom can have the same set of four quantum numbers. The principle arises from the fact that an orbital has a maximum occupancy of two electrons and their spins are paired.

penetration

The phenomenon in which an outer electron moves through the region occupied by the core electrons to spend part of its time closer to the nucleus; penetration increases the average effective nuclear charge for that electron.

periodic law

A law stating that, when the elements are arranged by atomic mass, they exhibit a periodic recurrence of properties.

shielding

The ability of other electrons, especially those occupying inner orbitals, to lessen the nuclear attraction for an outer electron.

transition element

An element that occupies the d block or the f block (inner transition element) of the periodic table

valence electrons

The electrons involved in compound formation; in main-group elements, the electrons in the valence (outer) level.

alloy

A mixture with metallic properties that consists of solid phases of two or more pure elements, a solid-solid solution, or distinct intermediate phases

bond energy (BE)

(also bond enthalpy or bond strength) The standard enthalpy change (always > 0) accompanying the breakage of a given bond in 1 mol of gaseous molecules

bond length

The distance between the nuclei of two bonded atoms.

bond order

The number of electron pairs shared by two bonded atoms

bonding pair

(also shared pair) An electron pair shared by two nuclei; the mutual attraction between the nuclei and the electron pair forms a covalent bond.

Born-Haber cycle

A series of hypothetical steps and their enthalpy changes that converts elements to an ionic compound; it is used to calculate the lattice energy

Coulomb's law

A law stating that the electrostatic energy between particles A and B is directly proportional to the product of their charges and inversely proportional to the distance between them:

covalent bond

A type of bond in which atoms are bonded through the sharing of electrons; the mutual attraction of the nuclei and an electron pair that holds atoms together in a molecule.

covalent bonding

The idealized bonding type that is based on localized electron-pair sharing between two atoms with little difference in their tendencies to lose or gain electrons (most commonly nonmetals)

double bond

A covalent bond that consists of two bonding pairs; two atoms sharing four electrons in the form of one σ and one π bond.

electronegativity (EN)

The relative ability of a bonded atom to attract shared electrons

electronegativity difference (ΔEN)

The difference in electronegativities between two bonded atoms.

electron-sea model

A qualitative description of metallic bonding proposing that metal atoms pool their valence electrons in a delocalized "sea" of electrons in which the metal ions (nuclei and core electrons) are submerged in an orderly array.

infrared (IR) spectroscopy

An instrumental technique for determining the types of bonds in a covalent molecule by measuring the absorption of IR radiation

ion pair

A gaseous ionic molecule, formed when an ionic compound vaporizes

lattice energy Δ H ° lattice

The enthalpy change (always positive) that accompanies the separation of 1 mol of a solid ionic compound into gaseous ions.

Lewis electron-dot symbol

A notation in which the element symbol represents the nucleus and inner electrons and surrounding dots represent the valence electrons

lone pair

(also unshared pair) An electron pair that is part of an atom's valence level but not involved in covalent bonding

metallic bonding

An idealized type of bonding based on the attraction between metal ions and their delocalized valence electrons.

nonpolar covalent bond

A covalent bond between identical atoms in which the bonding pair is shared equally

octet rule

The observation that, when atoms bond, they often lose, gain, or share electrons to attain a filled outer level of eight electrons (or two for H and Li)

partial ionic character

An estimate of the actual charge separation in a bond (caused by the electronegativity difference of the bonded atoms) relative to complete separation

polar covalent bond

A covalent bond in which the electron pair is shared unequally, so the bond has partially negative and partially positive poles

single bond

A bond that consists of one electron pair.

triple bond

A covalent bond that consists of three bonding pairs, two atoms sharing six electrons; one σ and two π bonds

axial group

An atom (or group) that lies above or below the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule.

bond angle

The angle formed by the bonds joining the nuclei of two surrounding atoms to the nucleus of the central atom, which is at the vertex

dipole moment (μ)

A measure of molecular polarity; the magnitude of the partial charges on the ends of a molecule (in coulombs) times the distance between them (in meters).

electron deficient

Referring to a bonded atom, such as Be or B, that has fewer than eight valence electrons

electron-pair delocalization

(also delocalization) The process by which electron density is spread over several atoms rather than remaining between two