Chapter 6 Section Review Questions
(3) Compound B has lower melting and boiling points than compound A. At the same temperature, compound B vaporizes faster than compound A. If one of these compounds is ionic and the other is molecular, which would you expect to be molecular? ionic? Explain your reasoning.
"In fact, many molecular compounds are already completely gaseous at room temperature. In contrast, the ions in ionic compounds are held together by strong attractive forces, so ionic compounds generally have higher melting and boiling points than do molecular compounds." Page 193(215 of 971) Compound B= Molecular compound(Vaporizes faster and has a lower boiling/melting point) Compound A= Ionic compound(Vaporizes slower and has a higher boiling/melting point)
(4) What is the relationship between metallic bond strength and enthalpy of vaporization?
"The amount of energy as heat required to vaporize the metal is a measure of the strength of the bonds that hold the metal together. The enthalpy of vaporization is defined as the amount of energy absorbed as heat when a specified amount of substance vaporizes at constant pressure."
(4) Explain why most metals are malleable and ductile but ionic crystals are not.
"The malleablility and ductility of metals are possible because metallic bonding is the same in all directions throughout the solid. When struck, one plane of atoms in a metal can slide past another without encountering resistance or breaking bonds. By contrast, recall from Section 3 that shifting the layers on an ionic crystal causes the bonds to break and the crystal to shatter."
(3) Use electron-dot notation to demonstrate the formation of ionic compounds involving the following: Li and Cl Ca and I
(Do On Paper/Tablet)
(4) Describe the electron-sea model of metallic bonding.
(FIGURE 18)(Page 195, 217 of 971) The model shows a portion of the crystal structure of solid sodium. The atoms are arranged so that each sodium atom is surrounded by eight other sodium atoms. The atoms are relatively fixed in position, while the electrons are free to move throughout the crystal, forming an electron sea.
(2) Define: Bond length and Bond energy
Bond length-The distance between two bonded atoms at their minimum potential energy, that is, the average distance between two bonded atoms Bond energy- energy required to break a chemical bond and form neutral isolated atoms
(2) State the octet rule
Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest occupied energy level
(1) INTERPRETING CONCEPTS Compare the following two pairs of atoms: Cu and Cl;I and Cl. a. Which pair would have a bond with a greater percent ionic character? b. In which pair would Cl have the greater negative charge?
Cu=1.90 I=2.66 Cl=3.16 3.16-1.90=1.26 (Cu & Cl) 3.16-2.66=0.50 (I & Cl) a. Cu & Cl has a greater percent ionic character b. In the I & Cl pair, Cl would have the greater negative charge
(2) APPLYING MODELS Compare the Molecules H2NNH2 and HNNH. Which moecule has a stronger N-N bond?
HNNH has a stronger N-N bond because it is a double bond, which is stronger than the single bond N-N bond in H2NNH2.
(3) Distinguish between ionic and molecular compounds in terms of the basic units that each is composed of
Molecular compound- a chemical compound whose simplest units are molecules Ionic compound- composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal
(1) What is the main distinction between ionic and covalent bonding?
Ionic bonding- Chemical bonding that results from the electrical attraction between cations and anions Covalent bonding- From the sharing of electron pairs between two atoms
(1) How is electronegativity used in determining the ionic or covalent character of the bonding between two elements?
It depends on the difference of electronegativities between the two atoms involved. If the electronegativity difference is between the atoms is between: 0-0.3=Non-polar Covalent Bond 0.31-1.7=Polar Covalent Bond 1.7-3.3=Ionic Bond
(4) ORGANIZING IDEAS Explain why metals are good electrical conductors.
Metals are good electrical conductors because of their free-moving sea of electrons that allow it to transfer electricity(or electrons) easily without impediment from ionic or molecular bonding.
(3) Give two examples of an ionic compound.
MgCl2 and NaCl
(3) ANALYZING DATA The melting points for the compounds Li2S, Rb2S, and K2S are 900degrees Celcius, 530 degrees Celcius, and 840 degrees Celcius, respectively. List these three compounds in order of increasing latice energy.
Rb2S(530), K2S(840), Li2S(900)
(2) How many pairs of electrons are share in the following types of covalent bonds? a. single bond b. double bond c. triple bond
a. 2 electrons b. 4 electrons c. 6 electrons
(1)INFERRING RELATIONSHIPS The isolated K atom is larger than the isolated Br atom. a. What type of bond is expected between K and Br? b. Which Ion in the compound KBr is larger?
a. Ionic Bond b. K is the largest ion in the compound KBr
(1) What type of bonding would be expected between the following atoms? a. U and F b. Cu and S c. I and Br
a. U=1.38 F=3.98 3.98-1.38=1.8 Ionic Bond b. Cu=1.90 S=2.58 2.58-1.90=0.68 Polar Covalent Bond c. I=2.66 Br= 2.96 2.96-2.66=0.3 Non polar Covalent Bond
(1) List the three pairs of atoms referred to in the previous question in order of increasing ionic character of bonding between them.
c.,b.,a. (Non-Polar Covalent Bond, Polar Covalent Bond, Ionic Bond)
