Period 3—2011
UNIT 6
Equations and Constants:
•
E = hf
•
KE = ½mv2
•
c = fλ
•
λ=
•
•
•
•
c = 2.9979 × 108 m/s
h = 6.626 × 10-34 J•s
me = 9.11 × 10-31 kg
NA = 6.022 × 1023
By Jake Grodsky and Sarine Hagopian
Covalent Bonds
-Formed when e- pairs are shared amongst atoms
-Generally a metal and a nonmetal pair
Key Terms
-Lewis structure: representation of a covalently
bonded molecule and its valence electrons
-Octet Rule: In a covalent molecule, each atom has
eight electrons around each atom
-Lone Pair: pair of e-s not involved in bonding
-Bond pair: pair of e-s shared between two atoms
-Double bond: two pairs of e-s shared between atoms
-Triple bond: three pairs of e-s shared between atoms
*As the number of shared e- pairs goes up Bond
length goes down
Electromagnetic Spectrum:
-Infared: 700+ nm
-Red: 630-700 nm
-Orange: 590-630 nm
-Yellow: 560-590 nm
-Green: 490-560 nm
-Blue: 450-490 nm
-Violet: 400-450 nm
-Ultraviolet: -less than 400 nm
Lewis Structures
-Symmetrical arrangements are more likely than
asymmetrical ones
-The less electronegative atom tends to be in the
middle
-Subtract valence e-s from total electrons needed to
complete octet/duet and divide by two  this is the
number of bonds that will need to be made
-If e- needed > e- remaining add bonds
-If e- remaining > e- needed add lone pairs to
central atom
Atomic Radius: Size of an atom which is influenced by the volume of the
e- orbitals (clouds)
Why does atomic radius increase as you go down a group?
-More energy levels so the new levels are “blocked” and therefore not as
tightly pulled to the center
Why does atomic radius decrease as you go across a period?
-Only one p+ and one e- are added
-Increasing nuclear charge pulls outermost e-s closer and closer to the
nucleus  reduces atom size
-All additional e- go into same principle energy level so shielding is not an
issue  nucleus just gets stronger and squeezes everything closer
Ionic Size:
-Cations are smaller than their neutral parent atoms
-Cations have more protons than electrons (hence their positive charge)
Protons more tightly pull the electrons towards the nucleus therefore
reducing the size of the atom
-Anions are larger than their neutral parent atoms
-Anions have more electrons than neutrons (hence their negative charge)
-Electrons are not as attracted to the nucleus therefore increasing atomic
radius
Number of Electron
Domains
2
Electron
Geometry
Linear
3
Trigonal Planar
4
Tetrahedral
5
Trigonal
Bipyramidal
6
Octahedral
Ionization Energy: amount of energy needed to remove an efrom an atom or ion
Electronegativity: a measure of the ability of an atom in a
chemical compound to attract/gain e-s
-As you go down a group, more orbitals are added  valence eare farther from nucleus so pull of p+s on the e-s is reduced
-As you go across a period, more protons are added to the
nucleus  valence electrons are held more tightly
Bonding
Pairs
2
3
2
4
3
2
Non-Bonding
Pairs
0
0
1
0
1
2
5
0
4
3
2
6
5
4
1
2
3
0
1
2
Molecular
Geometry
Linear
Trigonal Planar
Bent
Tetrahedral
Trigonal Pyramidal
Bent
Trigonal
Bipyramidal
Seesaw
T-Shaped
Linear
Octahedral
Square Pyramidal
Square Planar
sp
Bond
Angle
180º
sp2
120º
sp3
109.5º
sp3d
120º
90º
sp3d2
90º
90º
Hybridization