1.3- Bonding

Question 1

Give the definition of ionic bonding, and explain what makes the bonding stronger

Answer 1

Ionic bonding is the electrostatic force of attraction between oppositely charged ions formed by electron transfer

Ionic bonding is stronger when the ions are smaller, and/or have higher charges

Question 2

Explain how radii changes for positive and negative ions

Answer 2

Positive ions are smaller compared to thier atoms because it has one less shell of electrons and the ration of protons to electrons has increased to there is greater net force on the remaining electrons, holding them more closely

Negative ions formed from groups five to seven are larger than the corresponding atoms, the negative ion has more electrons but same number of protons, the pull of nucleus is shared over more electrons and attraction per electron is less making the ion bigger

Question 3

Explain ionic radii going down a group

Answer 3

The size of the ionic radii increases when going down a group, this is because when you go down a group the ions have more shells of electrons

Question 4

Give the definition of a covalent bond and a dative covalent bond

Answer 4

A covalent bond is a shared pair of electrons

A dative covalent bond forms when the shared pair of electrons in the covalent bond come from only one of the bonding atoms, a dative covalent bond is also known as a co-ordinate bond

Question 5

Give 3 examples that contain a dative covalent bond

Answer 5

NH4+, H30+ and NH3BF3

Question 6

Give the definition of metallic bonding

Answer 6

Metallic bonding is the electrostatic force of attratioin between the positive metal ions and the delocalised electrons

Question 7

what are the 3 factors that affect the strength of the metallic bonding

Answer 7

The number of protons/the strength of nuclear attraction

Number of delocalised electrons per atom, the more delocalised electrons the stronger the bond

The size of the ion, the smaller the ion the smaller the bond

Question 8

Give the 3 types of bonding, and explain the structure of each while giving examples

Answer 8

Ionic- The structure is a giant ionic lattice, examples include NaCl and MgO

Covalent- Simple molecular that are held together with intermolecular forces such as van der waals and hydorogen bonding, examples include I2, H2O and CO2

Covalent- Macromolecular, a giant molecular structure that is held together by strong covalent bonds, examples include diamond and graphite

Metallic- Giant metallic lattice, examples include magnesium and sodium

Question 9

Explain the boiling points and melting points of the four different structures

Answer 9

Ionic- High because of the giant lattice of ions with strong electrostatic forces of attraction between the oppositely charged ions

Molecular - Low because of the weak intermolecular forces between the molecules, van der waals etc

Macromolecular- Because of many strong covalent bonds in a macromolecular structure, it takes a lot of energy to break these many strong bonds

Question 10

Explain the solubility in water for the four structures

Answer 10

Ionic- Generally good

Molecular- Generally poor

Macromolecular- Insoluble

Metallic- Insoluble

Question 11

Explain the conductivity when molten and solid for the four structures

Answer 11

Ionic-
. Conductivity poor when solid, ions cannot move
. Conductivity is good when molten as the ions can move

Molecular-
. Poor, no ions to conduct
. Poor

Macromolecular-
. Diamon and sand are poor as electrons are localised and cannot move, however graphite is good as free deloclaised electrons between the layers
. Poor

Metallic
. Good, delocalisd electrons can move through structure
. Good

Question 12

Give the all the molecule shapes that contain no lone pairs

Answer 12

Linear, 2 bonding pairs, 180 deg

Trigonal planar, 3 bonding pairs, 120 deg

Tetrahedral - 4 bonding pairs, 109.5 deg

Trigonal bipyramidal, 5 bonding pairs, 120 and 90 deg

Octahedral, 6 bonding pairs, 90 deg

Question 13

Give the 2 variations of tetrahedral

Answer 13

Trigonal pyramidal, 3 bond pairs, 1 lone pair, 107 deg

Bent, 2 bond pairs, 2 lone pairs, 104.5 deg

Question 14

Give the definition of electronegativity

Answer 14

Electronegativity is the relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself

Question 15

What are the factors that affect electronegativity

Answer 15

Electronegativity increases across a period as the number of protons increases and the atomic radius decreases because the electrons in the same shell are pulled in more, it decreass down a group because the distance between a nucleus and the outer electrons increases and the shileding of inner electrons increases.

Question 16

Explain how electronegativity plays a role in the type of bonding that occurs

Answer 16

. Compounds with a large electronegativity difference will be purely ionic
. Compounds with a very similar electronegativity difference will be purely covalent

Question 17

What is a permanent dipole

Answer 17

A polar covalent bond is formed when elements have different electronegativities, when a bond is polar there is an unequal distribution of electrons in the bond and this produces charge seperation ends that are + and -

Question 18

What happens to the polarity in symmetric molecules

Answer 18

A symmetric molecule, with all bonds that are identical and no lone pairs will not be polar even if the bonds are polar

The dipoles all cancel out because it is symetrical

Question 19

Expalin what van der waals forces is and how it occurs

Answer 19

. They occur in all molecular substances and not ionic substances

. In a molecule the electrons are moving constantly , as this happens the electron density fluctuates and some parts become less negative and more negative

. These dipoles cause dipoles to cause in the neighbouring molecules, these are called induced dipoles

Question 20

What are the factors that affect the size of van der waals

Answer 20

The more electrons there ae in the molecule the higher the chance that temporary dipoles will form, this makes the vdw stronger between the molecules and so boiling points will also be greater

Question 21

How does the shape of the molecule have an effect on the size of van der waals forces

Answer 21

Long chain alkanes have a larger surface area of contact between molecules for van der waals to form than compared to spherical shaped branched alkanes and so have stronger van der waals

Question 22

How do permanent dipole dipole forces occur in a molecule

Answer 22

.Occurs in polar molecules
.Stronger that van der waals forces so the compounds have higher boiling points
. Polar molecules have a permanent dipole
. They are asymmetrical and have a bond where there is a signigicant difference in the electronegativity between the atoms

Question 23

What is hydrogen bonding

Answer 23

.Occurs in compounds that have a hydrogen atom attached to one of the three most electronegative elements F, O, N

. They must have an available lone pair, there is a large electronegativity difference between the H and the FON

Question 24

what is the bond angle in the hydrogen bond

Answer 24

180 deg

Question 25

Explain the difference in boiling point of molecules with the 3 different types of intermolecular forces

Answer 25

. Hydrogen bonding is the strongest intermolecular force, compounds that undergo hydrogen bonding have anomoulously high melting points

. Permanent dipole dipole is the second strongest intermolecular force

. Van der waals is the weakest type of intermolecular force out of the 3 intermolecular forces

Question 26

Draw the structure of ice, iodine, diamond, graphite, sodium chloride and magnesium

Answer 26

. Sodium chloride should be drawn in a lattice with negative ions bonded with positive ions

. Iodine should be drawn with 2 iodine molecules bonded through a covalent bond, and in space attracted by van der waals forces to the other iodine

. Diamond should be drawn in its specific macromolecular structure with 4 other carbons attached to each carbon, tetrahedral arrangement

. Graphite should be drawn in its specific macromolecular structure with 3 other carbons attached to it, in a plane arrangement

. Ice should be drawn with each water molecule being held together by hydrogen bonding, the hydrogen bonding should occur with the lone pair O and the hydrogen on the neighbouring molecule