CHEM 121 MODULE 4 EXAM QUESTIONS WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
Bonds (chemistry)
group of negatively charged valence electrons between the atoms that is simultaneously attracted by the positively charged nuclei of both atoms. (energy is released in the bond forming exothermic...
Bonds (chemistry)
group of negatively charged valence electrons between the atoms that is simultaneously
attracted by the positively charged nuclei of both atoms. (energy is released in the bond
forming exothermic reaction)
nonpolar covalent bond
a covalent bond in which the electrons are shared equally by the two atoms
single covalent bond
a bond formed when two atoms share a pair of electrons
double covalent bond
a bond in which two atoms share two pairs of electrons
triple covalent bond
a bond formed by sharing three pairs of electrons
0-0.5 electronegativity difference
non polar covalent bond (electrons shared equally)
0.5-1.6 electronegativity difference
polar covalent bond
Lewis Dot Structure
diagram of a molecule using dots to represent valence electrons
how to draw lewis dot structure
1. determine total # of valence e- for molecule by summing the # of valence e- for the
atoms, each atom has a # of valence e- equal to its group #
2. position atoms w/ least EN on inside and more EN on outside (H always on outside
and on an O atom if present) since H can only form a bond to one atom
3. put 2 e- between each set of atoms to form a bond
4. position the rest of the valence e- around the outside of the outer atoms (except H) to
complete octets of those atoms above or below (but not between the inner/outer atoms)
, 5. if any e- left, position them on the central atom to complete its octet, if central atom
still doesn't have an octet then move sets of e- from outside of outer atoms to between
the central to create a multiple bond
structural formulas from lewis structures
transition each pair of e- between atoms into a line. one pair = 1 line referred to as a
single bond. 2 pairs = 2 lines, 3 pairs = 3 lines.
lewis structures of polyatomic atoms
drawn similar except 1+ electron is lost or added which is implied by the positive or
negative charge
shape of a molecule
-- the position of the outer atoms relative to the central atom. how many outer atoms
can be seen occupying positions around the central atoms as determined by the
electron geometry.
-- if every group of electrons has an outer atom associated with it then the position of
every group of electrons is seen due to that associated atom and the shape is the same
as the electron geometry
-- in many cases there are 1+ groups of electrons that don't have an outer atom which
they are bonding to the central atom, these are called NONBONDED or UNSHARED
electrons since they're not bonding 2 atoms together and so that pair of electrons (and
that corner of the electron geometry) isn't seen because only the atoms are seen
VSEPR
valence shell electron pair repulsion: when atoms in molecules share e-'s to form bonds
these pairs of valence e-'s (because they're negatively charged) repel each other and
move as far away from one another as possible
PF5, SF6, XeF4
theres more than an octet rule P has 10, S has 12, Xe has 12, this is possible since
theyre filling valence e- which contain d orbitals and therefore can hold up to 18e-
tetrahedral e- geometry
central atom with surrounding groups of electrons arrange at corners of tetrahedron
pyramid with triangle base
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