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



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

Can you please explain how to get the answer for each question
thank you in advance

Answer 1

1. The first link is always a sigma bond. Next (double) must be pi bond. Sigma
bond is always the same, pi bonds may be two, two delta connections, too. If the
bond between two atoms is double, and there one sigma and one pi bond. If triple
- one sigma and two pi. If the quaternary - one sigma, two pi and delta, and so
on.
2. In acetylene bond between the atoms of carbon triple (one sigma and
two pi). And each of the carbon atoms bound to hydrogen atoms by a single bond
(ie sigma). So 1+1+1 = 3.
3. The more polar the molecule, the more common
electron pair is shifted to one of the atoms, ie, the higher the effective
charges of the atoms and the longer the length of the dipole. Therefore, in a
series of similarly constructed molecular dipole moment increases as the
difference between the electronegativities of the atoms that form the molecule.
For example, the dipole moments of HC1, HBr, and HI are, respectively, 1.04,
0.79 and 0,38 D, which is associated with a decrease in the difference between
the electronegativities of the atoms in the transition from HCl to HBr and НI.
So TeCl4 has dipol moment.