Chp. 2 Vocab Flashcards
atomic mass unit (amu)
A measure of atomic mass; 1/12 of the
mass of an atom of C12.
atomic number (Z)
For a chemical element, the number of
protons within the atomic nucleus.
atomic weight (A)
The weighted average of the atomic masses
of an atom’s naturally occurring isotopes. It may be expressed
in terms of atomic mass units (on an atomic basis), or the mass
per mole of atoms.
Bohr atomic model
An early atomic model in which electrons
are assumed to revolve around the nucleus in discrete orbitals.
bonding energy
The energy required to separate two atoms
that are chemically bonded to each other. It may be expressed
on a per-atom basis or per mole of atoms.
coulombic force
A force between charged particles such as
ions; the force is attractive when the particles are of opposite
charge.
covalent bond
A primary interatomic bond that is formed by
the sharing of electrons between neighboring atoms.
electron configuration
For an atom, the manner in which possible
electron states are filled with electrons.
electronegative
For an atom, having a tendency to ACEPT valence
electrons. Also used to describe nonmetallic elements.
electron state (level)
One of a set of discrete, quantized energies
that are allowed for electrons. In the atomic case, each
state is specified by four quantum numbers.
electropositive
For an atom, having a tendency to RELEASE valence
electrons. Also used to describe metallic elements.
ground state
A normally filled electron energy state from
which an electron excitation may occur.
hydrogen bond
A strong secondary interatomic bond that exists
between a bound hydrogen atom (its unscreened proton)
and the electrons of adjacent atoms.
ionic bond
A coulombic interatomic bond that exists between
two adjacent and oppositely charged ions.
isotopes
Atoms of the same element that have different atomic
masses.
metallic bond
A primary interatomic bond involving the nondirectional
sharing of nonlocalized valence electrons (“sea of
electrons”) that are mutually shared by all the atoms in the metallic solid.
mole
The quantity of a substance corresponding to 6.022x10^23
atoms or molecules.
Pauli exclusion principle
For an individual
atom, at most two electrons, which necessarily have opposite
spins, can occupy the same state.
periodic table
The arrangement of the chemical elements with
increasing atomic number according to the periodic variation
in electron structure. Nonmetallic elements are positioned at
the far right-hand side of the table.
polar molecule
A molecule in which there exists a permanent
electric dipole moment by virtue of the asymmetrical distribution
of positively and negatively charged regions.
primary bonds
Interatomic bonds that are relatively strong and
for which bonding energies are relatively large. Primary bonding
types are ionic, covalent, and metallic.
quantum mechanics
. A branch of physics that deals with atomic
and subatomic systems; it allows only discrete values of energy.
By contrast, for classical mechanics, continuous energy
values are permissible.
quantum numbers
A set of four numbers, the values of which
are used to label possible electron states. Three of the quantum
numbers are integers that specify the size, shape, and
spatial orientation of an electron’s probability density; the
fourth number designates spin orientation.
secondary bonds
Interatomic and intermolecular bonds that
are relatively weak and for which bonding energies are
relatively small. Normally, atomic or molecular dipoles are
involved. Examples of secondary bonding types are van der
Waals forces and hydrogen bonding.
valence electrons
The electrons in the outermost occupied electron
shell, which participate in interatomic bonding.
van der Waals bond
A secondary interatomic bond between
adjacent molecular dipoles that may be permanent or
induced.
wave mechanical model
An atomic model in which electrons
are treated as being wavelike.
