Bonding - Part 1

Question 1

Electronegativity

Answer 1

Ability of an atom to

attract a bonding pair of electrons in a covalent bond

towards itself

Question 2

Elements that are highly electronegative?

Answer 2

Oxygen and Fluorine

Question 3

Dipole

Answer 3

a pair of equal and oppositely charged poles

separated by a distance.

Question 4

Explanation if electrons are shared equally in a compound?

Answer 4

Produces a NON-POLAR covalent bond.

Purely covalent character.

(electronegativity difference between the two atoms is minimal. Eg H—H

Question 5

Explanation if electrons are unequally shared in a compound?

Answer 5

Produces a POLAR covalent bond.
Covalent bond with a little bit of ionic character Eg. H—F

(large electronegativity difference - between two atoms is between 0.4 to 2.0 then electrons are unequally shared as one atom pulls electrons more strongly, forming a dipole)

Question 6

Explanation when an electron is transferred from one atom to another?

Answer 6

Occurs if large difference in electronegativity between two atoms (eg. Between 2 and 4)

Forms an ionic bond

Exist as separate ions, no distortion of electron cloud

Question 7

Explain the bonding in carbon dioxide?

Answer 7

O=C=O

Symmetrical shape cancels out dipole with otherwise would form between C and O

Question 8

Explain this bond H—F?

Answer 8

The difference in the electro negativity of the two atoms causes a dipole.

polar covalent bond
partial ionic character

Question 9

Isoelectronic ions

Answer 9

Ions which have the same electron configuration. (Number of electrons)

Question 10

Why does atomic radius decrease from N to Al (or down a group of isoelectronic ions)

Answer 10

Atomic number increases
Nuclear charge increases
Number of shells and electrons stays same
Greater electrostatic attraction between outer shell electron and nucleus
Smaller ionic radius

Question 11

Two things that are evidence for the existence of ions?

Answer 11

1) The MPs of group 1 chlorides decrease down the group. This is because there are more shells and electrons so a larger atomic radius so a weaker attraction so less energy is required to break the ionic bonds.
2) Electrolysis provides evidence because The migration of coloured ions towards the respective electrodes and the coloured elements formed at each electrode proves the existence of separate ions.

Question 12

What does a higher ionic charge mean?

Answer 12

Stronger ionic bond
Eg. Na5+ has lost 5 electrons
Larger positive charge
OR COULD U SAY: lost more shells which decreases the ionic radius so the distance between the two attracting ions is smaller so the bond is stronger. ???????¿¿¿

Question 13

How does ionic radius relate to strength of ionic bond?

Answer 13

larger ionic radius
weaker ionic bond
because the more distance between the two attracting ions.

Typically it is the ionic radius of the cat ion (+) that has an effect on the strength of the bond. Why???????????

Question 14

Non-polar definition

Answer 14

Electrons are evenly distributed so that no separate positive or negative poles form.

Question 15

Polar definition

Answer 15

Electrons are unevenly distributed so separate negative and positive poles form.

Question 16

Dative covalent bond definition

Answer 16

A covalent bond when the shared pair of electrons come from only one of the bonding atoms.

Eg. Ammonium ion, usually ammonia has a lone pair of electrons on its nitrogen

In the ammonium ion the nitrogen provides both of its lone electrons to hydrogen ion to form the dative covalent bond.

Question 17

Why does the size of isoelectronic ions decrease

Answer 17

across a period of isoelectronic ions
number of electrons stays the same
number of protons in the nucleus increases (atomic number)

stronger attraction between the electrons and the protons in the nucleus
ionic radius decreases

Question 18

ionic bond

Answer 18

electrostatic attraction between two oppositely charged ions

Question 19

covalent bond

Answer 19

electrostatic attraction between positive nuclei of the atoms and their shared pair of electrons

Question 20

What happens to the size of isoelectronic ions across a period?

Answer 20

they decrease

Question 21

what happens to the size of ionic radius as you go down the group?

Answer 21

it increases because as you go down because you are adding more shells filled with electrons which all repel each other

(and maybe because all ions have the same charge so as shells increase there is a weaker attraction between the protons in the nucleus and their electrons)

Question 22

Why is there a big jump up in ionic radius as you go from 3+ ions (group 3) to 3- ions (group 5)?

Answer 22

because a whole layer of electrons is added.

eg. these ions are in period 3:
Al 3+ = 10 electrons (2,8)
P 3- = 18 electrons (2,8,8)

Question 23

Migration of ions example in U shaped drying tube

Answer 23

CuCrO4 (copper chromate)

blue colour of Cu2+ ions migrates to negative electrode
yellow colour of CrO4 2- ions migrates to the positive electrode

Question 24

Migration of ions example on moist filter paper example

Answer 24

drop of purple potassium manganate solution on moist filter paper placed on microscopic slide.
Ends of the slide are connected to 24 V DC power supply.
After ten minutes the purple colour of the
MnO4 - ion migrates to positive electrode

Question 25

4 physical properties of ionic compounds

Answer 25

1) high mps and bps - SEABOCI (strong electrostatic attraction between oppositely charged ions)
2) conduct electricity when molten - ions free to move
3) doesn’t conduct electricity when solid - ions not free to move
4) brittle/ easy to cleave apart

Question 26

How is a bond formed?

Answer 26

the overlap of two orbitals

Question 27

How to draw a dative covalent bond in an ammonium ion

Answer 27

NH4, for bonds, one bond replaced by an arrow pointing towards the H to represent the atom donating a lone pair

Question 28

Explain the strength of multiple bonds

Answer 28

Nuclei joined by multiple double bonds have a greater electron density between them so there is a greater force of attraction between the nuclei and of the bonding atoms and their shared electrons.

There is therefore a shorter bond length and a greater bond strength.

Question 29

How many electrons in Boron’s outer shell in BCl3?

Answer 29

6 electrons - not an octet

Question 30

How many outer shell electrons does S in SF6 have?

Answer 30

12 electrons - not an octet

Question 31

4 things dative covalent bonds are found in

Answer 31

1) NH4+
2) Between chlorine and electron deficient aluminium in Al2Cl6 (AlCl3 molecules join together to form this dimer)
3) Dative covalent bonds are the bonds between water ligands and the central metal ion in hexaaqua ions of metals such as [Mg(H2O)6]2+ and [Fe(H2O)6]2+
4) H3O+

Question 32

How is the dot and cross diagram for dimer, Al2Cl6 drawn?

Answer 32

3 chlorines
2 alum
3 chlorines

where Cl = dot, Al = X

• each chlorine has one electron from aluminium
• each aluminium has three of its own electrons making up three pairs with three chlorine electrons (3 lots of X Dot) & one pair dative covalent pair of electrons from chlorine

Search this - Al2Cl6 displayed for another picture

Question 33

most and least electronegative elements

Answer 33

fluorine - most

caesium - least

Question 34

Pauling scale range?

Answer 34

0-4

Question 35

Trend in electronegativity across a period

Answer 35

increases, proton and nuclear charge increases across a period whilst the number of shells and electrons remains the same so there is a stronger attraction between the electrons and the nucleus.

Question 36

3 main factors affecting strength of metallic bonding

Answer 36

1) nuclear charge - more protons = stronger attraction with delocalised electrons
2) number of delocalised electrons per atom- more delocalised electrons = stronger bond
3) size of metal ion - smaller = stronger attraction