Chapter 8 Covalent Bonding
molecular formula
A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms.
polyatomic ion
A tightly bound group of atoms that has a positive or negative charge and behaves as a unit
nonpolar covalent bond
A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.
covalent bonds
Bonds created by sharing electrons with other atoms.
how is an electron dot structure used to represent a covalent bond?
an eds represents the shared pair of electrons of covalent bond by two dots
what info does a molecule's molecular structure give?
arrangement of various atoms in space or which atoms are covalently bonded to one another
how is a coordinate covalent bond different from other covalent bonds?
in a coord covalent bond , the shared electron pair comes from one of bonding atoms
what are three ways in which the octet rule can sometimes fail to be obeyed?
-can't be satisfied in molecules whose total number of valence electrons is an odd number - molecules in which an atom has fewer or more than a complete octet of valence electrons
molecular compound
A compound that is composed of molecules
polar covalent bond
A covalent bond in which electrons are not shared equally
coordinate covalent bond
A covalent bond in which one atom contributes both bonding electrons.
pi bond
A covalent bond in which the bonding electrons are most likely to be found in sausage-shaped regions above and below the bond axis of the bonded atoms
diatomic molecule
A molecule consisting of two atoms
polar molecule
A molecule in which one side of the molecule is slightly negative and the opposite side is slightly positive.
molecule
A neutral group of atoms joined together by covalent bonds
van der waals forces
The two weakest intermolecular attractions - dispersion interaction and Dipoloe forces
dispersion forces
The weakest of all molecular interactions that are caused by the motion of electrons.
vsepr
Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible
hydrogen bonds
Very weak bonds; occurs when a hydrogen atom in one molecule is attracted to the electrostatic atom in another molecule
triple covalent bond
a bond formed by sharing three pairs of electrons
sigma bond
a bond formed when two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting the two atomic nuclei
double covalent bond
a bond in which two atoms share two pairs of electrons
bonding orbital
a molecular orbital that can be occupied by two electrons of a covalent bond
dipole
a molecule that has two poles
unshared pair
a pair of valence electrons that is not shared between atoms
resonance structure
a structure that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion
what electron configurations do atoms usually achieve by sharing electrons to form covalent bonds?
in covalent bonds, electrons sharing usually occurs so that atoms attain the electron configurations of noble gases
how do the strengths of intermolecular attractions compare to the strengths of ionic bonds and covalent bonds?
intermolecular attractions are weaker than either ionic or covalent bonds
why do network solids have high melting points?
melting a network solid would require breaking covalent bonds throughout the solid
how are the melting points and boiling points of molecular compounds usually differ from those of ionic compounds?
molecular compounds tend to have relatively lower melting and boiling points than ionic compounds
dipole interactions
occur when polar molecules are attracted to one another
molecular orbitals
orbitals that apply to the entire molecule
what is an example of a diatomic molecule found in the earth's atmosphere?
oxygen
what info does a molecular formula provide?
shows how many atoms of each element a molecule contains
what kinds of info does a structural formula reveal about the compound it represents?
shows the arrangement of covalently bonded atoms
network solids
solids in which all of the atoms are covalently bonded to each other
bond dissociation energy
the energy required to break the bond between two covalently bonded atoms
how do electronegativity values determine the charge distribution in a polar covalent bond?
the more electronegative atom attracts electrons more strongly and gains a slightly negative charge , the less electronegative atom has a slightly positive charge
what are the only elements that exist in nature as uncombined atoms?
the noble gases (monatomic)
how can the vsepr theory be used to predict the shapes of molecules?
the repulsion btw electron pairs causes molecular shapes to adjust so that the valence electron pairs stay as far apart as possible