BIO - TERMS - ATOM Flashcards
addition polymer
A polymer in which the monomers link together without the elimination of any atoms.
arachno-boranes
Boranes with the formula BₙHₙ₊₆, consisting of a cage of boron atoms that is missing two or three corners.
atomic element
Elements that exist in nature with single atoms as their basic units.
atomic solids
Solids whose composite units are atoms; they include nonbonding atomic solids, metallic atomic solids, and network covalent solids.
Avogadro’s number
The number of ¹²C atoms in exactly 12 g of ¹²C; equal to 6.0221179 * 10²³.
balanced chemical equation
A symbolic representation of a chemical reaction; a balanced equation contains equal numbers of the atoms of each element on both sides of the equation.
body-centered cubic
A unit cell that consists of a cube with one atom at each corner and one atom at the center of the cube.
bonding pair
A pair of electrons shared between two atoms.
chemical element
A fundamental substance composed of atoms that have the same atomic number and behave the same way chemically.
chemical equation
A symbolic representation of a chemical reaction; a balanced equation contains equal numbers of the atoms of each element on both sides of the equation.
chemical symbol
A one- or two letter abbreviation for an element; listed directly below an element’s atomic number on the periodic table.
Coniguration
The three-dimensional arrangement of atoms bonded to a chirality center.
Constitutional isomers
Isomers that have their atoms connected in a different order. For example, butane and 2-methylpropane are constitutional isomers.
covalent radius (bonding atomic radius)
In nonmetals, one-half the distance between two atoms bonded together, and in metals one-half the distance between two adjacent atoms in a crystal of the metal.
crystalline lattice
The regular arrangement of atoms in a crystalline solid.
dehydrogenation
The loss of hydrogen atoms from a substrate.
diamagnetic
The state of an atom or ion that contains only paired electrons and is, therefore, slightly repelled by an external magnetic field.
disubstituted benzene
A benzene in which two hydrogen atoms have been replaced by other atoms.
electron affinity (EA)
The energy change associated with the gaining of an electron by an atom in its gaseous state.
electronic configuration
The arrangement of electrons in shells or energy levels in an atom.
empirical formula molar mass
The sum of the masses of all the atoms in an empirical formula.
energy level
Potential energy of an electron in an atom. See also electron shell.
ferromagnetic
The state of an atom or ion that is very strongly attracted by an external magnetic field.
Geiger–Müller counter
A device used to detect radioactivity, which uses argon atoms that become ionized in the presence of energetic particles to produce an electrical signal.
hexagonal closest packing
A closest-packed arrangement in which the atoms of the third layer align exactly over those in the first layer.
Hydride shift
The shift of a hydrogen atom and its electron pair to a nearby cationic center.
Hyperconjugation
An electronic interaction that results from overlap of a vacant p orbital on one atom with a neighboring C-H σ bond. Hyperconjugation is important in stabilizing carbocations and substituted alkenes.
interstitial alloy
An alloy in which small, usually nonmetallic atoms fit between the metallic atoms of a crystal.
ionization energy (IE)
The energy required to remove an electron from an atom or ion in its gaseous state.
lanthanide contraction
The trend toward leveling off in size of the atoms in the third and fourth transition rows due to the ineffective shielding of the f sublevel electrons.
lone pair
A pair of electrons associated with only one atom.
mass defect
The difference in mass between the nucleus of an atom and the sum of the separated particles that make up that nucleus.
metallic atomic solids
Atomic solids held together by metallic bonds; they have variable melting points.
metallic bonding
The type of bonding that occurs in metal crystals, in which metal atoms donate their electrons to an electron sea, delocalized over the entire crystal lattice.
molar mass
The mass in grams of 1 mol of atoms of an element; numerically equivalent to the atomic mass of the element in amu.
network covalent atomic solids
Atomic solids held together by covalent bonds; they have high melting points.
nido-boranes
Boranes that have the formula BₙHₙ₊₄ and consist of a cage of boron atoms missing one corner.
nonbonding atomic radius
The distance between the centers of adjacent atoms in direct contact but not bonded together.
nonbonding atomic solids
Atomic solids held together by dispersion forces; they have low melting points.
nonbonding orbital
An orbital whose electrons remain localized on an atom.
nuclear fission
The splitting of the nucleus of an atom, resulting in a tremendous release of energy.
nuclear theory
The theory that most of the atom’s mass and all of its positive charge are contained in a small, dense nucleus.
nuclide
A particular isotope of an atom.
octahedral hole
A space that exists in the middle of six atoms on two adjacent close-packed sheets of atoms in a crystal lattice.
packing efficiency
The percentage of volume of a unit cell occupied by the atoms, assumed to be spherical.
paramagnetic
The state of an atom or ion that contains unpaired electrons and is, therefore, attracted by an external magnetic field.
percent ionic character
The ratio of a bond’s actual dipole moment to the dipole moment it would have if the electron were transferred completely from one atom to the other, multiplied by 100%.
Periplanar
A conformation in which bonds to neighboring atoms have a parallel arrangement. In an eclipsed conformation, the neighboring bonds are syn periplanar; in a staggered conformation, the bonds are anti periplanar.
peroxide anion
An oxygen anion consisting of two atoms of oxygen (O2⁻²).
polyatomic ion
An ion composed of two or more atoms.
polypeptide backbone
Repeating sequence of atoms along the core of the polypeptide chain.
radioactive
The state of those unstable atoms that emit subatomic particles or high-energy electromagnetic radiation.
Re face
One of two faces of a planar, sp2-hybridized atom.
Rearrangement reactions
What occurs when a single reactant undergoes a reorganization of bonds and atoms to yield an isomeric product.
second (s)
The SI standard unit of time, defined as the duration of 9,192,631,770 periods of the radiation emitted from a certain transition in a cesium-133 atom.
Si face
One of two faces of a planar, sp2-hybridized atom.
silicates
Network covalent atomic solids that contain silicon, oxygen, and various metal atoms.
simple cubic
A unit cell that consists of a cube with one atom at each corner.
single bond
A covalent bond formed by sharing one electron pair between atoms.
sp hybrid orbitals
Hybrid orbitals derived from the combination of an s and a p atomic orbital. The two sp orbitals that result from hybridization are oriented at an angle of 180° to each other.
sp2 hybrid orbitals
Hybrid orbitals derived by combination of an s atomic orbital with two p atomic orbitals. The three sp2 hybrid orbitals that result lie in a plane at angles of 120° to each other.
sp3 hybrid orbitals
Hybrid orbitals derived by combination of an s atomic orbital with three p atomic orbitals. The four sp3 hybrid orbitals that result are directed toward the corners of a regular tetrahedron at angles of 109° to each other.
strong force
Of the four fundamental forces of physics, the one that is the strongest but acts over the shortest distance; the strong force is responsible for holding the protons and neutrons together in the nucleus of an atom.
Sulfonium ions
A species containing a positively charged, trivalent sulfur atom, R3S+.
tetrahedral hole
A space that exists directly above the center point of three closest-packed metal atoms in one plane and a fourth metal located directly above the center point in the adjacent plane in a crystal lattice.
Valence shell
The outermost electron shell of an atom.
van der Waals radius (nonbonding atomic radius)
One-half the distance between the centers of adjacent, nonbonding atoms in a crystal.
Wave equation
A mathematical expression that deines the behavior of an electron in an atom.
X-ray diffraction
A powerful laboratory technique that allows for determining the arrangement of atoms in a crystal and for measuring the distance between them.
