Post on 04-Jan-2016
Chapter 6 Review
Test: Friday December 09, 2011
Be sure to know the following terms
• Chemical bond• Nonpolar covalent bond• Polar covalent bond• Chemical formula• Unshared (lone) pair• Resonance• Polyatomic ions
What is the most electronegative element on the periodic table? • Fluorine (F)
What is the least electronegative element on the periodic table?• Cesium (Cs)
According to the rules of drawing Lewis structures, which atom is the central atom?• The least
electronegative atom
Use electronegativity differences to determine whether each of the following bonds is nonpolar covalent, polar covalent, or ionic. Determine the
direction of polarity.
H—F Na—Cl4.0 – 2.1 =1.9 3.0 – 0.9 = 2.1
H—O N—N3.5 – 2.1 = 1.4 3.0 – 3.0 = 0
H—C H—N2.5 – 2.1 = 0.4 3.0 – 2.1 = 0.9
Ba—O C—O 3.5 – 0.9 = 2.6 3.5 – 2.5 = 1.0
Define single bond, double bond, and triple bond. List them in order
of increasing bond energy…Increasing bond length.
• Single bond: bond in which one pair of electrons is shared (C--C)• Double bond: bond in which two pairs of electrons are shared (C=C)• Triple bond: bond in which three pairs of electrons are shared • BEsingle > double > triple• BL triple > double > single
Compare and contrast ionic and covalent compounds.
CovalentElectrons are shared
Atoms vibrateSmallest unit called
moleculeLow melting/boiling points
WeakerNonmetal+nonmetal
IonicBond between ionsIons cannot move
Smallest unit called formula unit
High melting/boiling points
Solutions can conduct electricity
StrongerMetal + nonmetal
The manner in which ions lower their potential
energy and stabilizing ionic compounds by
combining in an orderly arrangement is called….• Crystal lattice
What is the octet rule? • Outer energy level with 8 electrons
Name exceptions to the octet rule.• Hydrogen, boron• Oxygen, fluorine, chlorine
What is meant by expanded valence? Which elements can have an expanded valence?
• An outer energy level with more than 8 electrons
• The most electronegative elements Cl, F, O
What is the amount of energy required to separate bonded atoms into neutral
atoms?•Bond energy
What is the amount of energy required to separate an ionic compound into its
constituent ions?•Lattice energy
Metallic Bonding• The highest energy levels of most metal atoms are
occupied by very few electrons. For example s-block metals contain only 1 or 2 electrons and all three p orbitals are empty.
• Within a metal, the vacant orbitals in the atoms’ outer energy levels overlap. This overlapping of orbitals allows the outer electrons of the atoms to roam freely throughout the entire metal the electrons do not belong to any one atom but move freely about the metal’s network of empty atomic orbitals (sea of electrons)
METALLIC BONDING (CONT’D)* The chemical bonding that results from the attraction between metal atoms and the surrounding sea of electronsThe freedom of electrons to move in a network accounts for the properties of metals: electrical and thermal conductivity, absorption/reflection of light, luster, malleability, ductility
Metallic Bonding• Metal atoms in electron
sea• Good conductors• higher melting
point/boiling point• Overall “negative” charge
due to moving electrons• Can be shaped: malleable
and ductile
Ionic Bonding• Cations and anions in
crystal lattice• Solution/molten state
good conductors• Lower melting/boiling
points• Bonded ions form
neutrally charged compound
• Hard and brittle
Enthalpy of vaporization• Enthalpy = heat• Just as lattice energy represents the
strength of an ionic bond, enthalpy of vaporization represents the strength of a metallic bond
*amount of energy (as heat) required to vaporize the metal
Intermolecular Forces(forces of attraction between molecules)
-vary in strength, but generally weaker than covalent, metallic, and ionic bonds1. dipole: created by equal but opposite charges
separated by a short distance-occurs when a slightly negatively charged atom
in a polar bond is attracted to a slightly negatively charged atom in a nearby molecule
Intermolecular Forces (cont’d)2. Hydrogen bonding: intermolecular force in which a hydrogen atom that is bonded to a highly electronegative atom is attracted to an unshared pair of electrons of an electronegative atom in a nearby molecule
Intermolecular Forces (cont’d)
3. London dispersion forces: intermolecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles*act between ALL molecules and atoms*ONLY intermolecular forces acting among noble gases and nonpolar molecules* Strength of LDFs increasing with increasing atomic or molar mass (more specifically—increasing # of electrons)
Arrange the following attractions in order of increasing strength: covalent, ionic,
metallic, dipole-dipole, hydrogen bonding, London dispersion
1. London dispersion2. Dipole-dipole3. Hydrogen bonding4. Nonpolar covalent5. Polar covalent6. Ionic7. Metallic
Symbol Ion Commonly Formed
Number of Electrons in Ion Z
Te 54In 49Sr Sr2+
Mg2+ 12ClF 9
Be2+ 2Br 36Al 13O
Chemical Symbol
Main Group Number
Group Name
Metal or Nonmetal
Charge of ion formed
K metal
Br halogens
Sr 2+
He 8A
Na Alkali metals
Cl 7A
Mg metal
Xe N/A
O chalcogens
Rb 1+
Which of the following pairs of elements do you expect to be most
similar? Why?(a) Ti and Ga(b) N and O(c) Li and Na(d) Ar and Br(e) Ge and Ga
Predict the ion formed by each of the following. How many electrons
will be gained OR lost?• Rb• K• Al• O• F• N• Mg• C• B
electron
neutron
proton
Classify the following elements as atomic or molecular.
• Xenon• Iodine• Oxygen• Nickel
Classify each of the following compounds as ionic or molecular.
CS2 CuOKI PCl3PtO2 COSO3 H2O
What are the basic units—atoms, molecules, or formula units—that
compose each of the following substances?
BaBr2 Rb2O NONe CF4 N2
I2 N2F4 O3
CO NaCl HBr
Use electron-dot notation to illustrate the number of valence electrons present in one atom of each of the following elements.
Rb C OP B ClLi N TeAr Ca AsGa Ge At
In writing Lewis structures, how is the need for multiple bonds
generally determined?• The need for a multiple bond becomes obvious if there are not enough valence electrons to complete octets by adding unshared pairs.•Multiple bonds are possible in Lewis structures containing C, N, or O.
What is a formula unit? What are the
components of one formula unit of CaF2?
• Smallest whole unit of an ionic compound
• Ca2+ and 2 F-
What type of energy best represents the strength of an ionic bond?
What type of bonding holds a polyatomic ion together?
How does bond length relate to bond energy?
What is the relationship of heat of vaporization of a metal and the strength of the bonds that hold the metal together?
A chemical bond between atoms results from the attraction between the valence electrons of one atom and the ________ in the _________ of another atoms.• Protons; nucleusAtoms with a strong attraction for electrons they share with another atom exhibit ________.• High electronegativityBonds that possess between 5% and 50% ionic character are considered to be _________.• Polar covalentThe greater the electronegativity difference between two atoms bonded together, the greater the bond’s percentage of _________.• Ionic character
The electrons involved in the formation of a chemical bond are called ____________.
If a bond’s character is more than 50% ionic, then the bond is called a(n) ________________.
How can electronegativity be used to distinguish between an ionic and covalent bond?
In a crystal of an ionic compound, each cation is surrounded by a number of _________.
Compared with the neutral atoms involved in the formation of an ionic compound, the crystal lattice that results is _________ in potential energy.
VSEPR valence shell electron-pair repulsion
Identify the major assumption of the VSEPR theory that is used to predict the shape of atoms.• Electrons are located as far apart as possible
because of electron-electron repulsion
In the VSEPR theory, double and triple bonds are treated the same as single bonds.
AB2
AB3
AB4
AB2E
AB3E
AB2E2
BeF2
BF3
ONFCH4
NH3
H2O