The ________ represents the quantity of energy required to break a chemical bond.
bond energy
12.1
When electrons in a molecule are shared between atoms, either evenly or unevenly, a(n) _________ bond is said to exists.
covalent
12.1
What does it mean to say that a bond is polar? Give two examples of molecule withe polar bonds. Indicate in your examples the directions of the polarity.
A bond is polar if the centers of positives and negative share do not coincide at the same point. The bond has a negative end and a positive end. Any molecule in which the atoms in the bond are not identical will have polar bonds (although the molecules as a whole may not be polar). Two simple examples are HCl and HF.
12.2
What factors determines the relative level of polarity of a polar covalent bond?
The difference in electronegative between the atoms in the bond.
12.2
In each of the following groups which element is the most electronegative? Which is the least electronegative?
a. Rb, Sr, I
b. Ca, Mg, Sr
c. Br, Ca, K
(a) I is most electronegative, Rb is least electronegative
(b) Mg is most electronegative, Ca and Sr have similar electronegative
(c) Br is most electronegative, K is least electronegative
12.2
Which of the following molecules contain polar covalent bonds?
a. sulfur, S8
b. fluorine, F2
c. iodine monochloride, ICl
d. hydrogen bromide, HBr
c and d
12.2
Which bond in each of the following pairs has less ionic character?
a. Na Cl or Ca-Cl
b. Cs-Cl or Ba-Cl
c. Fe-I or Fe-F
d. Be-F or Ba-F
a. Ca-Cl
b. Ba-Cl
c. Fe-I
d. Be-F
12.2
In each of the following diatomic molecules which end of the molecule is positive relative to the other end?
a. hydrogen fluoride, HF
b. chlorine monofluoride, ClF
c. iodine monochloride, ICl
a. H
b. Cl
c. I
12.3
For each of the following bonds draw a figure indicating the direction of the bond dipole, including which end of the bond is positive and which is negative
a. P-F c. P-C
b. P-O d. P-H
a. +P --> F-
b. +P -->O-
c. +P -->C-
d. P H (H and P have essentially the same electronegative)
12.3
The metallic element lose elections when reacting, and the resulting positive ions have an electron configuration analogous to the _________ noble gas.
preceding
12.4
Which simple ion would each of the following element be expected to form? Which noble gas has an analogous electron configuration to ear of the ions?
a. bromine, Z= 35
b. cesium, Z= 55
c. phosphorus, Z= 15
d. sulfur, Z= 16
a. Br- [Kr]
b. Cs+ [Xe]
c. P�3- [Ar]
d. S�2- [Ar]
12.4
On the basis of their electron configurations, predict the formulas of the simple binary ionic compound likely to form when the following pairs of elements react with each other.
a. Na and S
b. Ba and Se
c. Mg and Br
d. Li and N
e. K and H
a. Na2 Se
b. BaSe
c. MgBr2
d. Li3 N
e. KH
12.4
Name the noble gas atom that has the same electron configuration as each of the ions in the following compounds.
a. SrO
b. CaH
c. K3 P
d. BaSe
a. S�2+ [Kr]; O�2- [Ne]
b. Ca�2+ [Ar]; H�- [He]
c. K�+ [Ar]; P�3- [Ar]
d. Ba�2+ [Xe]; Se�2- [Kr]
12.4
Why are anions always larger than the atoms from which they are formed?
In forming an anion, an atom gains additional electrons in its outermost (valence) shell. Having additional electron in the cadence shell increases the repulsive forces between electrons, and the outermost shell becomes larger to accommodate this.
12.5
For each of the following pairs, indicate which is larger.
a. I or F
b. F or F-
c. Na+ or F-
a. I
b. F-
c. F-
12.5
Explain what the "duet"and "octet" rules are and how they are used to describe the arrangement of electrons in a molecule.
When atoms form covalent bonds, they try to attain a cadence-elctron configuration similar to that of the following noble bass element. When the elements in the first few horizontal rows of the periodic table for covalent bonds, they attempt to achieve the configuration of the noble gases helium (two valence electrons, duet rule) and neon and argon (eight valence electrons, octet rule).
12.6 and 12.7
When elements in the second and third periods occur in compounds, what number of electrons in valence shell represents the most stable electron arrangement? Why?
These element at ton at total of eight cadence electrons, giving the valence-electron configuration of the noble gases Ne and Ar.
12.6 and 12.7
What does it mean when two atoms in a molecule are connected by a "double bond"? Write the Lewis structure of a molecule containing a double bond.
Two atoms in a molecule are connected by a triple bond if the atoms share three pairs of electrons (six electrons) to complete their outermost shells. A simple molecule containing a triple bond is acetylene, C2H2 (H:C:::C:H:)
12.6 and 12.7
What is the geometric structure of the ammonia molecule? How many pair of electron surrounding the nitrogen atom in NH3? What is the approximate H N H bond angle in ammonia?
The geometric structure of NH3, is a trigonal pyramid. The nitrogen atom if NH3 is surrounded by your electron pairs (three are bonding, on is a lone pair). The H-N-H bond and is about 109.5 (because of the presence of the lone pair).
12.8
What is the geometric structure of SiF4 molecule? How many pairs of valence electrons are present on the silicon atom of SiF4? WHat are the approximate F Si F bond angles in SiF4?
SiF4 has a tetrahedral geometric structure; eight pairs of electrons on Si, it is about an 109.5 angle
12.8
What general principles determine the molecular structure (shape) or a molecule?
The general structure of a molecule is determined by how many electron pairs surround the central atom in the molecule, and by which of those pairs are used for bonding to the other atoms of the molecule.
12.9
Why are all diatomic molecules linear, regardless of the number of valence electrons pairs not he atom involved?
The geometry shows that only two points in a space are needed to indicate a straight line. A diatomic molecule represents two point in space.
12.9
Although both BF3 and NF3 molecule contain the same number of atoms, the BF3 molecule is flat, whereas the NF3 molecule is trigonal pyramidal. Explain.
In NF3, the nitrogen atom has four pairs of valence electrons; in BF3, only three pairs of valence electrons surrounding the boron atom. The nonbonding pair on nitrogen in NF3 pushes the three F atoms our of the plan of the N atom.
12.9
Using the VSEPR theory, predict the molecular structure of each of the following molecules.
a. CCl4
b. H2S
c. GeI4
a. tetrahedral
b. bent (nonlinear)
c. tetrahedral
12.9
When two atoms share two pairs of electrons a(n) _________ bond is said to exist between them.
double
AdP
In each case, which of the following pairs of bond elements forms the more polar bond?
a. S-F or S-Cl
b. N-O or P-O
c. C-H or Si-H
a. S-F
b. P-O
c. C-H
AdP
For each of the following pairs of elements, identify which element would be expected to be more electronegative. It should not be necessary to look at a table of actual electronegativity values.
a. Be or Ba
b. N or P
c. F or Cl
a. Be
b. N
c. F
AdP
Using the VSEPR theory, predict the molecular structure of each of the following polyatomic ions.
a. chlorate ion
b. chlorite ion
c. perchlorate ion
a. trigonal pyramid
b. nonlinear
c. tetrahedral
AdP