Chemical Bonding and Structure

Question 1

Component metals, properties and uses of Steel

Answer 1

Iron and Carbon

High tensile strength but corrodes

Used a s structural material

Question 2

Component metals, properties and uses of Stainless steel

Answer 2

Iron, Nickel and Chromium

Strong and resistant to corrosion

Domestic and industrial appliances

Question 3

Component metals and uses of Brass

Answer 3

Copper and zinc

Pluming fittings and instruments

Question 4

Component metals and uses of Bronze

Answer 4

Copper and tin

Coins, medals, and tools

Question 5

Component metals and uses of Pewter

Answer 5

Tin, antimony and copper

Decorative objects

Question 6

Component metals, properties, and uses of Duralumin

Answer 6

Aluminum, copper and manganese

Strong, light and resistant to corrosion

Aircrafts, boats, and Machinery

Question 7

Component metals and uses of Nichrome

Answer 7

Nickel and copper

Heating elements in toasters and electric heaters

Question 8

Component metals, properties and uses of Solder

Answer 8

Lead and tin

Low mp

Joining of two metals in electric circuits

Question 9

Component metals and uses of Sterling silver

Answer 9

Silver and copper

Jewellery and art objects

Question 10

What dictates wether a bind is ionic?

Answer 10

If the difference in electro negativity is GREATER than 1.8

Question 11

What is a coordinate bond?

Answer 11

When the electrons in a shared pair of electrons between two atoms comes from just one of those atoms

Question 12

What is the relationship between bond length and bond strength

Answer 12

The shorter the bond the stronger the bond.

Question 13

How do binds become polar?

Answer 13

This occurs when a shaheed pair of electrons are not shared equally as one atom has a higher electronegative attracting the electrons more. The atom which attracts the electrons more is marked with a negative sigma.

Question 14

What does VSPER theory state?

Answer 14

Electron domains arrange themselves around the central atom such that they are as far apart from each other as possible.

Question 15

Name the shape and bond angle when a molecules has this many number of domains (all bonded) :

-2
-3
-4
-5
-6

Answer 15

2 - linear, 180°
3 - trigonal planar,120°
4 - tetrahedral, 109.5°
5 - trigonal bipyramidal, 90°, 120° and 180°
6 - octahedral, 90° and 180°

Question 16

Shape of a molecule with three domains (2 bonding, 1 non bonding) and the bond angle

Answer 16

Bent, V-Shapped

Bond angle less than 120° as repulsion between non binding pair is greater

Question 17

Shape of a molecule with 4 domains (3 bonding, 1 non bonding) and the bond angle

Answer 17

Trigonal pyramidal

Less than 109.5° as repulsion caused by non binding pair is greater

Question 18

Shape of a molecule with 4 domains (2 bonding, 2 non bonding) and the bond angle

Answer 18

Bent, V- Shaped

Less than 109.5° and less than bond angle in 3 bonding 1 non binding as two non binding cause greatest repulsion

Question 19

Shape of a molecule with 6 domains (4 bonding, 2 non bonding) and the bond angle

Answer 19

Square planar

90° bond angle

Question 20

Shape of a molecule with 5 domains (4 bonding, 1 non bonding) and the bond angle

Answer 20

See-saw

120° and 90°

Question 21

Shape of a molecule with 5 domains (3 bonding, 2 non bonding) and the bond angle

Answer 21

T - shape

90°

Question 22

What are resonance hybrids ?

Answer 22

When a molecule can be written as two or more different forms in Lewis structures

Question 23

Evidence for resonance structures

Answer 23

In Ozone (O3) the bond length between the supposedly double bonded and single bonded oxygen atoms are equal length and an intermediate length to a typical single or double bond of oxygen atoms

Question 24

When is a molecule polar?

Answer 24

When the differences in electronegative between atoms causes a resultant dipole (doesn’t cancel out due to its shape)

Question 25

What are London dispersion forces?

Answer 25

This is caused by a momentarily in even dispersion of electrons, forming an instantaneous dipole. This can induce a dipole into a neighboring molecule resulting in a weak attraction between the molecules.

Question 26

What causes London dispersion forces to increase in strength and why?

Answer 26

An increase in mass of the molecule as it will have more electrons and thus a greater chance of having an unequal dispersion of electrons

Question 27

What are INTER and INTRA molecular forces?

Answer 27

Inter molecular forces are the weak forces of attraction between molecules where as intra refer to the strong attractive forces inside a covalently bonded molecule

Question 28

What are van der waals forces made up of and love them in order of strength.

Answer 28

London dispersion - weakest

Dipole - dipole induced

Dipole - dipole - strongest

Question 29

What is hydrogen bonding and how does it occur?

Answer 29

When hydrogen is bonded to O, F, N the electronegative differences between those elements and hydrogen cause hydrogen to remain as a single proton. This is attracted to a lone pair of an atom of F, N or O forming an INTER molecule dipole - dipole attraction

Question 30

How does a sigma bond form?

Answer 30

When two s, one s one p or two p orbitals overlap head on along a line drawn through the nucleus of both atoms

Question 31

How does a pi bond form?

Answer 31

A pi bond forms when two p orbitals overlap sideways above and below the line so if which sigma bonds form. It is formed by two regions of electron density.

Question 32

How and why may electrons be delocalized

Answer 32

When a molecule has a resonance structure electrons become delocalizad as this is most energetically favorable.

Question 33

Formula for formal charge

Answer 33

Number of valance electrons - number of non binding electrons - 1/2(number of bonding electrons)

Question 34

Using formal charge how do we deduce the most favorable structure of a molecule

Answer 34

The sum of the total formal charge of individual atoms closest to 0 is favorable.

If both structure have the same sum. The molecule with the most molecules closest to zero is favored.

Question 35

How does ozone form

Answer 35

O2 —-(high energyUV light—-> 2O•

2O• + O2 —-> O3

Question 36

How does ozone break down (chemical equation)

Answer 36

O3 —-(low energy UV light)—-> O2 + O•

O3 + O• —-> 2 O2

Question 37

Why is the Ozone layer depleting

Answer 37

The formation and break down of ozone happens at a steady state, however, CFCs and Nitrogen oxidizes disrupt this balance, depleting the ozone

Question 38

When do molecules have an sp3, sp2 and sp hybridization?

Answer 38

sp3 occurs when one atom is bonded to 4 other atoms or atoms and electron pairs (methane)

sp2 occurs when one atom is bonded to 3 other atoms or electron pair (seen in ethene)

sp occurs when one atom is bonded with two other atoms or electron pairs(ethyne)

Question 39

How many sigma bonds and pi bonds in a:

Single bond

Double bond

Triple bond

Answer 39

Single pond - sigma bond

Double bond - one sigma one pi bond

Triple bond - one sigma two pi bond

Question 40

Explain sp3 hybridisation wit reference to methane

Answer 40

When the carbon bonds in methane one o its 2s electrons is promoted to a 2p orbital and then the 2s and three 2p orbitals hybridise to form our new hybrid orbitals. These four new orbitals arrange themselves to be as mutually repulsive as possible, i.e. tetrahedrally. Four equal sigma bonds can then be formed with the hydrogen atoms

Question 41

Explain sp2 hybridisation with reference to ethene

Answer 41

After a 2s electron on the carbon atom is promoted the 2s orbital hybridizes with two o the 2p orbitals to form three new planar hybrid orbitals with a bond angle of 120º between them. These can form sigma bonds with the hydrogen atoms and also a sigma bond between the two carbon atoms. Each carbon atom now has one electron remaining in a 2p orbital. These can overlap to form a pi bond. Ethene is thus a planar molecule with a region of electron density above and below the plane.

Question 42

Explain sp hybridisation wit reference to ethyne

Answer 42

sp hybridization occurs when the 2s orbital hybridizes with just one of the 2p orbitals to form two new linear sp hybrid orbitals with an angle of 180º between them. The remaining two p orbitals on each carbon atom then overlap to form two pi bonds.

Question 43

Which elements can expand their octets?

Answer 43

An element from Period 3 and below will be able to expand octet by making use of its energetically accessible, or low lying d-subshell for bonding