Chemical Bond

Question 1

What e- take part in chemical bonds

Answer 1

Valence e-

Question 2

What are chemical bonds

Answer 2

Chemical bonds=interactions that account for the association of atoms into molecules, ions and crystals

Question 3

Why do atoms form chemical bonds

Answer 3

To achive more stable electronic confoguration

Question 4

What impact do chemical bonds have on the energy of the system

Answer 4

They minimize the total energy of the system

Question 5

What does miminun of the potential energy curve corresponds to

Answer 5

Bond formation. The deeper the curve is=stronger the bond

Question 6

What is the bond energy

Answer 6

Measure of bond strength of a chem.bond. it is the amount of energy needed to break the atoms involved in chem.bond into free atoms

Question 7

What is bond length

Answer 7

It is defined as the mean distance between the centers of 2 atoms in a molecule. The smaller the distance=more stable the bond

Question 8

What is bond angle

Answer 8

Angle between 2 bonds, usually measured in degrees

Question 9

What is bond angle related to

Answer 9

Dimension and electronegativity of the atoms forming a bond

Question 10

How can e- behave in a bond

Answer 10

1. It can be shared=>non electrostatic bond; covalent bond
2. It can be transfered from one atom to another=>electrostatic bond; ionic bond

Question 11

Explain polarity of covalent bonds

Answer 11

If the atoms have same electronegaticity is is non polar covalent bond.(H-H)
If they have different electronegativity e- isn’t located exactly on the middle but closer to the nucleus of more electronegatice atom which forms dipoles. That is polar covalent bond

Question 12

What is Lewis structure

Answer 12

Bidimensional representation of the structiral formula and it doesnt give information abt 3D structure

Question 13

Explain how is Lewis structure written

Answer 13

Dots are used for valence e-.Lines are drawn for bonds. Lond pairs are drawn as pair of dots

Question 14

Characteristic of ionic compounds

Answer 14

-solid crystals
-high melting temperature
-the melted compound conducts electrcity
-they can dissolve in water and comduct electricity

Question 15

Explain formation of crystalline solid

Answer 15

There is forces of attraction between opposite charges and repulsion between similiar charges and that orients an ion in such way where positive ion is surrounded by negative ions and vice versa. They are arranged in such manner that positive and negative charges alternate and balance each other, overall charge of the substance being zero

Question 16

What is lattice energy

Answer 16

Energy change upon formation of a crystalline ionic compound from its constituent gaseous ions

Question 17

What does binding in covalent bond arises from

Answer 17

Electrostatic attraction of both nuclei for the same electrons

Question 18

Some characteristic of covalent bond

Answer 18

It is directional and it gived definitive shapes. It is very strong bond

Question 19

What is coordinate covalent bond

Answer 19

When both e- come from the same atom
Ex. (H+) + (NH3)=(NH4+)

Question 20

What is octet rule

Answer 20

Tendency of an atom in a molecule to have 8e- in the valence shell

Question 21

What does it mean when some element is electron deficient and hypervalent

Answer 21

Electron deficient is when atom in a molecule doesnt have a full octet
And hypervalent is whem it has expanded octet

Question 22

Why would some molecule be radical

Answer 22

When it has 1 unpaired e-(ex. NO-one e- in N is unpaired,N is e- deficient)

Question 23

What is electronegativity difference in bonds

Answer 23

In non polar covalent /\X=0
In polar covalent /\X=0.9
In ionic /_\X =2.1

Question 24

What is bond order

Answer 24

Number of bonds between 2 atoms
•Single bond=two atoms share 1 couple of e-(bond order of 1)
•Multiple bond= the atoms share 2 or more couple of e-
°Double bond-bond order 2
°Triple bond-bond order 3

Question 25

What is isolated atom

Answer 25

Number of e- associated with the atom is the same ad number of valence e-

Question 26

What is formal charge

Answer 26

Difference between the number of valence e- in a free atom and number of e- assigned to the atom in the Lewis structure
Formar charge= valence e- - number of bonds - number of unshared e-

Question 27

How does determination of Lewis structure works

Answer 27

1. Determine the total number of valence e- in the molecule. This will be sum of the valence e- of all atoms + charge
2. Choose a central atom(the least electronegative one or the atom with the highest valence)
3. Draw skeletal structure connecting the atoms with 1 bond
4. Add the rest of the e- to the outside atoms. And the left over e- to the central atom
5. Check if everyone has a full octet. If the central one doesnt have a full octet, a lone pair from a peripheral atom may be pushed to create double or triple bonds
6. Determine formal charges and decide which structure is the most probable

Question 28

What is prefered Lewis structure

Answer 28

-one with fewer number of formal charges
-with less formal charges
-charges should match electronegativity

Question 29

What is resonance

Answer 29

It is used when no single Lewis structure accuratly represents the observing bonding in a molecule. The actual structure is represented by an avarage of several resonance forms

Question 30

How are resonance forms showed

Answer 30

With double-headed arrow between them

Question 31

Do resonance forms have independent existance

Answer 31

No. The real steicture is avarage of the resonance forms and there is not an equilibrium or osciallation between them