Covalent bonding ( Chemical Bonding)

Question 1

Between what elements do covalent bonds occur?

Answer 1

Between non metal and non metal and sometimes between metal and non metal.

Question 2

What is Covalent bond?

Answer 2

It is the electrostatic attraction between the nuclei of two atoms and the shared pair of electron in the other atom.

Question 3

What overlaps in a covalent bond?

Answer 3

The atomic orbitals overlap in a covalent bond. Thus an S orbital can overlap with a P orbital.

Question 4

What is bond length?

Answer 4

It is the distance between two nuclei of covalently bonded atoms.

Question 5

What is the relation between bond energy and bond lenght?

Answer 5

Bond energy and bond length are inversely related. Longer the bond length easier to break and requires less energy.

Hence the bigger the atoms are the bigger the bond length and easier for atoms to break the bond. Smaller the atoms, smaller the bond length and more energy needed to break bond.

Question 6

What is molecule and cmopound?

Answer 6

Molecules contain two or more atoms bonded together while compounds contain 2 or more different atoms bonded. Thus every covalent compound is a molecule but not every molecule is a compound.

Question 7

What happens to bond energy with molecules going down the group?

Answer 7

F,Cl,Br,I ( down the group) . The atom size increases bond length increases and the bond strength decreases. Also the more shells an atom has the more indistinct its shell becomes so the orbitals with more shells bond “ineffectively”. (lecture 4 15 mins)

Question 8

Why is F2 bond weaker in comparison to Cl and Br even though F2 should be stronger since its smaller.

Answer 8

Fluorine’s atom size is so small that nucleus start to repel it, when shells overlap hence making the bond weaker.

Question 9

What is a sigma bond??

Answer 9

Covalent bond formed after orbitals overlap horizontally or head on overlapping.

Every single bond created is a sigma bond.

Question 10

which period acquires noble gas configuration and which has an expanded octet?

Answer 10

period 2 - noble gas config

period 3- expanded octet

Question 11

why can period 3 elements expand their octets?

Answer 11

They have unfilled p and d orbitals.
compounds sulfur dioxide,
SO2, phosphorus pentachloride, PCl 5 , and sulfur hexafluoride, SF6

Question 12

Which elements have limited octet?

Answer 12

Group 2 and 3 elements. though they can complete octet with dative bonding.

Question 13

What is a pi bond?

Answer 13

In pi bond orbitals overlap sideways and not head on. if atoms have more than two bonds between them one is pi if there are 3 2 are pi

Question 14

How many bonds can an atom make?

Answer 14

The number of unpaired electrons it has.

Question 15

What is hybridization?

Answer 15

The formation of hybrid orbitals

Question 16

What is the case in which carbon makes 4 sigma bonds?

Answer 16

This means that the carbon has gone through sp3 hybridization, since carbon has only 2 unpaired electrons, thus it has to hybridize and get 4 unpaired electrons in order to form 4 sigma bonds.

All C in alkanes are sp3 hybridized
All C in diamond are sp3 hybridized

Question 17

What kind of energy is in bond forming and bond making?

Answer 17

bond forming : exothermic

bond breaking : endothermic

Question 18

What is the case in which carbon makes 3 sigma and one pi bond?

Answer 18

It means that carbon is sp2 hybridized.
Thus in alkenes carbon is sp2 hybridized.
Each carbon in graphite is also sp2 hybridized

Question 19

Why does carbon occur in sp2 hybridization and not sp3?

Answer 19

When given a few hydrogens it can only form 3 sigma bond with hydrogens due to less hydrogen, and thus it is forced to form a pi bond. In excess hydrogen there are enough hydrogen to form 4 sigma bonds and thus sp3 hybridization occurs.

Question 20

What bonds form in the hybridized orbitals?

Answer 20

The sigma bonds always occur in the hybridized orbitals and the pi bonds occur in non hybridized orbitals.

Question 21

What is the case in which carbon makes 2 pi and 2 sigma bonds?

Answer 21

In this state carbon forms sp orbital. This is because the carbon does not have enough atoms to bond to and thus forms bonds on its own.

Question 22

Which bonds are stronger between sigma and pi?

Answer 22

sigma bonds are consider stronger than pi bonds. Sigma is stronger because orbitals overlap linearly and head on and thus are more “effective”

Question 23

Why are alkenes reactive and alkanes not?

Answer 23

Alkenes owe their reactivity to pi bond, the pi bond is only made when enough atoms are not there to bond and thus as soon as the alkene gets a chance to form a bond it breaks the pi and forms sigma, Alkanes however are already bonded with all sigma bonds and thus need no further reaction.

Question 24

What is dative covalent bonding?

Answer 24

It is the electron transfer and then sharing of electrons between two atoms.

Question 25

what are conditions of dative bonding?

Answer 25

1) donor of electron should have at least one lone pair
2) One electronegative element can only form one dative bond irrespective of number of lone pairs
3) Acceptor of electron should have at least one empty orbital
4) Acceptor of electron can form more than one dative bond
5) once a dative bond forms shape of molecule and bond angle changes.

Question 26

How do we know when molecules form dative bonds?

Answer 26

Mostly they will stick together for eg. AlCl3 + AlCl3= Al2Cl6