Question

**1**Multiple bonding results from the sharing of more than one electron pair. An example of this phenomenon is the double bond. In this case, the second bond is characterized as:

a. a delta bond
b. a pi bond
c. a sigma bond
d. a second single bond





**2**How many sigma bonds are there in C2H2?

a. 4
b. 6
c. 3
d. 7
e. 5



**3**Molecules which are polar overall exhibit a property called a dipole moment. Which of the following molecules has a dipole moment?

a. SiCl4
b. AlI3
c. TeCl4
d. PF5
e. None of these


Can you please explain how to get the answer

Answer 1

Please i need help very quickly. I have a test over this stuff tomorrow
thank you in advance

Answer 2

I know #1 is b
#2 is c
#3 is c
but I dont know how to get the answers. Please help me

Answer 3

For #3 you need to figure out which of the compounds listed is a polar molecule. You can figure that out based upon the differences in electronegativity. A polar molecule will be one where an atom with a high electronegativity is covalently bonded with one with much lower electronegativity. Look at the periodic table. The closer an element is to Fluorine the higher its electronegativity is. ignore noble gases. If the atoms of the compound are very close to each other on the periodic table they should not be polar.

Answer 4

Also electronegativity decreases as you move down the periodic table. In this case most of the compounds have relatively close elements.

Answer 5

But I think all of the compounds in #3 are polar. How do we know if a compound has a dipole moment

Answer 6

Shape also matters. A dipole moment occurs when electron density is unequal across a molecule creating partial positive and negative charges. If the electrons are not shared equally on all sides a dipole can occur. This question is tricky. Aluminum and iodine are actually both pretty far from F so they would both have similar electronegativities. The only one with a big difference in electronegativity is SiCl4, which has a tetrahedral geometry. Since there are 4 Cl around it they would all be pulling the electrons in opposite directions equally so it would balance out.

Answer 7

Aluminum is trigonal planar and it has 3 iodides, so it balances.

Answer 8

phosphorus can share 5 electrons and Te can share 6, so Te is the only central atom with an unbalanced side.

Answer 9

For number 2 you would need to draw the molecule. You then count all the single bonds and one bond of a double or triple bond. Since carbon has to have 4 bonds and hydrogen can only have one, You should end up with a triple bond between the carbons, and one H attached to each carbon. That will give you a sigma bond with each carbon to hydrogen bond, and only one of the carbon-carbon triple bond= 3.