Chapter 8 Flashcards
Covalent bond
atoms share electrons
Molecule
neutral group of atoms joined by covalent bonds
Diatomic molecule
consisting of two atoms (e.g. oxygen molecule)
Molecular compound
a compound composed of molecules
Molecular compound melting point
relatively lower than those of ionic compounds
Molecular formula
chemical formula of a molecular compound, shows how many atoms of each element a molecule contains
Octet rule
atoms share to attain the electron configuration of noble gases
Single covalent bond
two atoms held by sharing a pair of electrons, shown by a bar
Double and triple covalent bonds
formed if the atoms can achieve the electron structure of noble gases
Coordinate covalent bond
a covalent bond in which one atom contributes both bonding electrons
Polyatomic ion
a tightly bound group of atoms that has a charge and behaves as a unit
Bond dissociation energies
the energy needed to break the bond between two covalently bonded atoms, large energy corresponds to a strong bond
A resonance structure
a structure that occurs when it’s possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion
Exceptions to the octet rule
cannot be satisfied in molecules whose total # of valence electron is an odd #
Molecular orbitals
when two atoms combine, this model assumes that their orbitals overlap to produce molecular orbitals
Molecular orbitals belong to
a molecule as a whole
Bonding orbital
a molecular orbital that can be occupied by two electrons of a covalent bond
Sigma
symmetrical molecular orbital
Pi
sausage-shaped molecular orbital, asymmetrical
VSEPR theory
the repulsion between electron pairs causes molecular shapes to adjust so that the valence electron pairs stay as far apart as possible
Orbital hybridization
provides information about both molecular bonding and molecular shape
What happens in hybridization?
several atomic orbitals mix to form the total # of equivalent hybrid orbitals
Non polar covalent bonds
when the atoms pull equally in the bond
Polar covalent bond
when the atoms pull unequally in the bond
The more electronegative atom
attracts electrons more strongly and gains a slightly negative chard
The less electronegative atom
has a slightly positive charge
Polar molecules
one end is slightly negative, the other end is slightly positive
Dipole
a molecule that has two poles
When polar molecules are placed between oppositely charged plates, what happens?
they tend to become oriented to the respective positive and negatively charged plates
Intermolecular attractions
weaker than with ionic or covalent bonds
Van der Waals forces
the two weakest attractions between molecules
Dipole interactions
when polar molecules are attracted to one another
Dispersion forces
weakest of all, caused by the motions of electrons
Hydrogen bonds
a hydrogen covalently bonded to a very electronegative atom is weakly bonded to an unshared electron pair of another electronegative atom
Network solids
solids in which all of the atoms are covalently bonded to each other
Melting a network solid
requires breaking covalent bonds throughout a solid
An example of a network solid
diamond
Widely varying intermolecular attractions cause
a great range of physical properties among covalent compounds
