3. Bonding in Compounds

Question 1

What are the 3 types of bonding found in compounds?

Answer 1

IONIC
POLAR COVALENT
NON-POLAR COVALENT

Question 2

What is an ionic bond?

Answer 2

An Ionic bond is the electrostatic attraction between a positive and a negative ion.

Question 3

How do metals and non metals gain a stable octet?

Answer 3

metals LOSE electrons to get a NOBLE GAS electron arrangement while non-metals GAIN electrons.

Question 4

Explain ionic compounds

Answer 4

Ionic compounds tend to form from METALS and NON-METALS.

Ionic compounds have HIGH melting and boiling points.

Ionic compounds therefore are always SOLID at room temperature.

Question 5

Why do ionic compounds not conduct when solid?

Answer 5

THE IONS ARE NOT FREE TO MOVE. They only conduct when MOLTEN or in SOLUTION.

Question 6

Where can ionic bonding not be found?

Answer 6

Ionic bonding cannot be found in elements. Elements are made of atoms.

Question 7

What are the 2 types of covalent compound?

Answer 7

molecular and network.

Question 8

What is an example of a covalent network?

Answer 8

Silicon Dioxide SiO2.

Question 9

Explain the structure of silicon dioxide

Answer 9

Each Si bonds to 4 O and each O bonds to 2 Si.

So the ratio is 2:4 so 1:2 and the formula is SiO2.

It’s a network so very high m.pt. and b.pt and very very hard and covalent bonds are very strong. SiO2 is sand, so used also in sand-paper.

Question 10

Why do covalent networks have high melting points?

Answer 10

Covalent network compounds have very HIGH melting points because it takes a lot of energy to break the very strong covalent bonds.

Question 11

Why are covalent networks very hard?

Answer 11

Covalent network compounds are very hard because it takes a lot of energy to break the very strong covalent bonds.

Question 12

How do atoms form covalent bonds?

Answer 12

by SHARING electrons

Question 13

If the electrons are shared equally i.e. sit in the MIDDLE of the bond what do we call it?

Answer 13

we call the bond a Non-polar Covalent Bond.

Question 14

What is a non-polar covalent/pure covalent bond?

Answer 14

If the electrons are shared equally i.e. sit in the MIDDLE of the bond

Question 15

What is a polar covalent bond?

Answer 15

Bonds in which the electrons are unequally shared are called Polar Covalent Bonds.

Question 16

Bonds in which the electrons are unequally shared are called what?

Answer 16

Polar Covalent Bonds.

Question 17

Explain Hydrogen Flouride?

Answer 17

H+ —- F-

The shared pair of electrons sit closer to the F than the H. The is why the F has a slightly negative charge δ-. This unequal sharing makes the polar bond. Sometimes also called a permanent dipole

Question 18

Why are Polar Covalent bonds existing?

Answer 18

This unequal sharing is due to a property called ELECTRONEGATIVITY.

Question 19

What is ELECTRONEGATIVITY?

Answer 19

Electronegativity is measure of the attraction that an atom has for the shared pair of electrons in a covalent bond.

Question 20

Explain the trends in ELECTRONEGATIVITY.

Answer 20

Electronegativity INCREASES across a PERIOD.

Electronegativity DECREASES down a GROUP.

Question 21

Explain why the electronegativity values increase across a period

Answer 21

1. As the atomic number goes up there are more protons added to the nucleus, so the nuclear charge goes up.
2. This stronger pull from the nucleus pulls the electrons in tighter
3. (so the atom and it’s covalent radius get smaller).
4. So the electronegativity must be higher due to the higher pull from the nucleus.

Question 22

Explain why the electronegativity values decrease down a group

Answer 22

1. As you go down the group you add extra shells of electrons, which makes the atoms bigger.
2. The atomic number also gets bigger so they also have a larger nuclear charge.
3. However the extra shells of electrons shield the outer electrons from the pull of the nucleus.
4. As it’s the outer electrons that are involved in bonding this means the electronegativity must decrease as they are now pulled in as tightly.

Question 23

Why can’t polar covalent bonding exist in an element?

Answer 23

1. As we are talking about elements all the atoms present must be the same.
2. So the electronegativity values are the same so the bonding electrons must be equally shared, so the bond must be non-polar.
3. You can’t get polar bonds in an element.

Question 24

Can polar covalent bonds exist in an element?

Answer 24

No.

Question 25

How do you determine if a compound has more ionic or covalent character?

Answer 25

Compounds with the greatest difference in electronegativities between the atoms will have more IONIC character.

Compounds with very little difference in the electronegativity values will be more COVALENT.

Question 26

What is the exception that has polar-covalent bonds?

Answer 26

TiCl4

Question 27

How do you determine the polarity from a structure?

Answer 27

If the distribution of polarity is equal across the whole molecule it is non-polar.

If the distribution is unequal (like in water) it will be polar.

Question 28

Explain the polarity and structure of Ammonia

Answer 28

It is polar.

N is negative, the 3 Hs are positive

Question 29

Explain the polarity and structure of carbon dioxide

Answer 29

It is non polar.
C is positive
2 O’s are double bonded and are negative

Question 30

Explain the polarity and structure of Chloroform

Answer 30

Polar
C+ in centre
Cl- x 3 branching out
H on top

Question 31

Explain the polarity and structure of carbon tetrachloride

Answer 31

Non-Polar
C + in centre
Cl- x 4

Question 32

Explain the polarity and structure of hydrogen sulphide

Answer 32

Polar.
- S in centre
H+ x 2

Question 33

If a molecule is polar we say that it has a?

Answer 33

PERMANENT DIPOLE.