Study Buddy: Chemical Bonding
Terms
Metallic Bond
Description
array of positively charged metal cores
surrounded by a sea of mobile or delocalized
valence electrons
Illustration
http://blogs.scientificamerican.com/lab-rat/2012/03/21/metallic-bonding/
electrostatic interactions between oppositely
charged ions (cation and anion)
Ionic Bond
http://wps.prenhall.com/wps/media/objects/439/449969/Media_Portfolio/ch08.html
Formula Unit: smallest unit of an ionic compound
Covalent Bond
formed when two or more nonmetals with similar
or small difference in electronegativities share
pair(s) of valence electrons in order to obtain the
electron configuration of a noble gas
http://bio1151.nicerweb.com/Locked/media/ch02/covalent_bond.html
Molecule: covalently bonded neutral groups of
atoms
Valence Shell
Electron Pair
Repulsion Theory
(VSEPR)
electron pairs repel both bonding and nonbonding
electrons resulting in a stable (lowest-energy),
three-dimensional geometry
http://www.molecularmodelscompany.com/Products/VSEPR/VSEPRtheorychart.aspx
http://www.schoolphysics.co.uk/age1114/Electricity%20and%20magnetism/C
urrent%20electricity/text/Electric_curren
t/index.html
http://socratic.org/questions/why-don-tionic-compounds-have-electricalconductivity-as-a-solid-but-they-do-as
Representations:
1. Draw and label a picture or diagram to explain why metals are electrically conductive as solids
and ionic compounds are when molten or in solution.
Metals are shown on the left
here and an ionic compound
on the right. Metals have free
electrons as solids (fig. 1a),
which move to conduct
electricity (fig. 1b). Ionic
compounds are explained
under their respective figures.
2. Why are metals malleable and ductile, but not ionic or covalently bonded compounds?
Metal’s free electrons allow their nuclei to slide by each other without enough repulsion between
adjacent nuclei to break apart the compound. Ionic and covalent compounds have more rigid
structures that do not allow atoms to move past each other without breaking.
11/16/15
SCIE_CHEM_BOND_MAT_STUDYBUDDYTE_AL
copyright © CFISD 2015
1
3. Identify these compounds as ionic or covalent, then draw Lewis dot diagrams for:
a. MgO
b. Na3N
c. Na2SO4
ionic
ionic
ionic
O
Mg2+ [ O ]2-
3 Na+ [ N ]3-
2 Na+
2-
O S O
O
Trigonal Planar
Tetrahedral
Linear
Lewis Dot
http://people.uwplatt.ed
u/~sundin/114/plco2.ht
m
f. BH3
covalent
http://www.chemeddl.org/resou
rces/models360/models.php?p
ubchem=6331
4.
e. O2
covalent
http://www.amazingrust.com/E
xperiments/how_to/Oxygen.ht
ml
http://imgarcade.com/1/l
ewis-dot-structure-forccl4/
d. CCl4
covalent
Trigonal
Pyramidal
Bent
http://people.uwplatt.
edu/~sundin/114/plnh
3.htm
http://blog.sciencematters.org/2012/0
4/10/drawinglewis-structures/
Examples
CO2,
diatomics
BH3, Boroncontaining
CCl4, CCl2F2
NH3, PF3
H2O, OF2
Polar
molecule?
Maybe
Maybe
Maybe
Yes
Yes
5. Why are VSEPR shapes used for molecules but not formula units?
Formula units represent a ratio of atoms involved in a larger, repeating crystalline structure.
Molecules are individual groups of atoms that can exist on their own. Hence, molecules can have
distinct 3D shapes, but formula units are just representing a part of a larger whole.
6. Why are scientists interested in VSEPR-related shapes of molecules and not simply their Lewis
dot structures?
Students may remember “structure and function” going together from Biology. This refers to the
structure of a compound being related to its biological function in living organisms. VSEPR can be
used to predict overall shape of biological compounds and inorganic compounds. Many material
properties are based on the shape of the compound and not simply its arrangement of bonded
and lone-pair electrons.
7. How can bonds in a molecule be polar, but the molecule be non-polar?
A bond is polar if the two elements unequally share the electrons. However, in symmetrical
VSEPR shapes, the polar bonds can “cancel out” each other and the overall molecule is non-polar
11/16/15
SCIE_CHEM_BOND_MAT_STUDYBUDDYTE_AL
copyright © CFISD 2015
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