Chemistry
STUDY GUIDE #4
Updated 1/9 /2011
Chemical Bonding and Compounds
A student who completes this unit should be able to do all of the following:
1) Define a chemical bond and related concepts:
a) Define chemical bond
b) Define bond energy
c) Define a compound
d) Define a chemical change (chemical reaction) in terms of bonds broken or bonds formed
e) Compare and contrast the properties of 2 separate elements (before they bond) with the
properties of a compound that they form (after they bond)
2) Distinguish between the two major types of bonding
a) Ionic bonding: electronegativity difference 1.7 or more, so electrons are stolen or transferred
b) Covalent bonding: electronegativity difference <1.7, so electrons are shared
i) polar covalent: electronegativity difference between 0.4 and 1.7, so:
electrons are shared unequally;
the bond has ends that are slightly positive and negative;
the separation of electrical charge is called a dipole
ii) nonpolar covalent: electronegativity diff. <0.4, so electrons are shared more equally and
no difference in charge can be detected between the two ends of the bond (no dipole)
3) Understand ionic bonding and the properties of ionic compounds
a) Define an ion: an electrically charged atom or group of atoms*
b) Define ionic bonding in terms of electron transfer (or theft) and coulombic force
c) Use the periodic table to predict:
i) if an element will form positive or negative ions
ii) the charge on the ion formed
iii) if an ionic bond will form between two elements
Octet rule: atoms achieve maximum stability with 8 valence electrons (or 2 in period 1)
d) Explain why and how ionic compounds form between two elements
e) Draw electron dot diagrams for ions and for ionic compounds
f) Use Coulomb’s law to calculate the relative force of attraction between two ions
in terms of ionic charges
in terms of ionic sizes and interatomic distance
g) Describe and explain some properties of ionic compounds
i) Build a model of an ionic compound, showing the crystal lattice structure
ii) Explain what the chemical formula of an ionic compound represents (ie. formula unit)
h) Write formulas for ionic compounds, given their names:
i) Binary compounds of main group elements and transition metals
ii) Compounds containing polyatomic ions
(SEE HANDOUTS ON NOMENCLATURE
iii) Special naming rules for acids
AND ON POLYATOMIC IONS)
iv) Hydrated compounds
i) Write names for ionic compounds, given their formulas:
i) Binary compounds
ii) Compounds containing polyatomic ions
iii) Special naming rules for acids
iv) Hydrated compounds
*NOTE: unless otherwise stated, atoms, elements and
compounds are always considered NEUTRAL;
CONTINUED on next page
ions are always CHARGED
STUDY GUIDE #4, continued:
4) Understand covalent bonding and the properties of covalent compounds
a) Define a covalent bond as a pair of shared electrons
i) Understand polar bonds (unequal sharing of electrons) & nonpolar bonds (roughly equal sharing)
ii) Understand double and triple bonds
b) Use the periodic table to predict if a covalent bond will form between two elements
c) Explain the properties of a covalent bond:
i) how the bond forms
ii) bond length
iii) bond energy (bond strength)
iv) orbital notation: sp, sp2, sp3, dsp3, d2sp3 hybridization
v) dipoles and their occurrence, and how to draw diagrams to show dipoles
d) Explain some unique properties of H2O in terms of:
i) bond polarity
ii) hydrogen bonding
iii) effects on solubility (“like dissolves like”, hydration shells)
iv) effects on boiling point and heat of vaporization, and their geological & biological consequences
v) density changes upon freezing, and their geological & biological consequences
e) Explain the nature of molecules and molecular compounds in terms of:
i) molecular formulas
ii) intermolecular forces (hydrogen bonding, Van der Waals, London) and melting points
iii) solubility – “like dissolves like”
f) Assign names to molecular compounds, and write formulas based on the names
(SEE HANDOUTS ON NOMENCLATURE)
g) Draw electron dot diagrams (Lewis structures) for covalent compounds, including those containing:
i) lone pairs of electrons
ii) single, double, and triple bonds; distinguish these in terms of bond length and
bond energy
h) Use VSEPR theory to predict the molecular geometry of covalent compounds
i) know different shapes: linear, trigonal planar, tetrahedral, trigonal bipyramid, octahedral
ii) know bond angles for each shape
iii) know degenerate forms of each shape, especially pyramidal and bent
iv) build models based on molecular geometry
v) predict whether or not a molecule will have a dipole (polar vs. nonpolar):
polarity of individual bonds
molecular symmetry, and overall polarity of the molecule
5) Calculate molecular weights, and use the mole concept in further calculations
a) Molecular weight
b) The mole; molar mass
c) Avogadro’s law: every mole has the same number of fundamental particles
nA = 6.022 *1023 molecules per mole
d) Molarity M = moles / liter
e) Percentage composition problems
f) Determining empirical formulas from percentage composition
i) understand empirical formulas
ii) understand that determining a true molecular formula requires more information
TEXT CHAPTERS: Ch. 6 and Ch. 7
MASSACHUSETTS CURRICULUM FRAMEWORKS, content standard #4
STUDY EVERY NIGHT, STARTING NOW. COME TO CLASS PREPARED.
REVIEW NOTES AND BOOK EVERY NIGHT. GET EXTRA HELP AFTER SCHOOL.
BE SUCCESSFUL. BE PREPARED. ASK QUESTIONS.
EXPECT MORE FROM YOURSELF. YOU CAN DO WELL IF YOU WANT TO.