Bonding And Sturcture

Question 1

What is the octet rule?

Answer 1

Atoms of elements join together so that each atom has 8 electrons in outer shell. Unpaired electrons pair up by sharing or transferring electrons resulting in each atom having the same electron configuration as a noble gas.

Question 2

What is ionic bonding?

Answer 2

Ionic binding is the electrostatic attraction between + and - ions.

Question 3

What do giant ionic bonds form between?

Answer 3

Metal and a non metal.
Electron transferred from the metal to the non metal. The ions then attract.

Question 4

How do metals form ions?
How do non metals form ions?

Answer 4

Metals lose electrons, form + ions.
Non metals gain electrons, form - ions.

Question 5

What are examples of compounds which are ionic?

Answer 5

Nitrate, carbonate, sulphate, ammonium etc.

Question 6

What do substances that have ionic bonding form?

Answer 6

Giant ionic lattice structure.
Positive and negaitive ions are held together by strong forces of electrostatic attractions between ions.

Question 7

Why are ionic compounds solid at room temp with a high mp and bp?

Answer 7

A large amount of energy is needed to break the electrostatic attractions between oppositely charged ions.

Question 8

Why can ionic bonding not conduct electricity when solid but when dissolved in water or when molten they are good conductors of electricity?

Answer 8

In solid state, ions are in a fixed position in the lattice and cannot move.
When molten/dissolved in water, the ions are free to move so electricity can flow.

Question 9

Why are ionic compounds soluble in polar solvents?

Answer 9

Polar molecules are attracted to the positive and negative ions in the ionic compound. The giant ionic lattice breaks down and the ions are surrounded by water molecules.

Question 10

Whats the definition for covalent bonding?

Answer 10

Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.

Question 11

Where do covalent bonds occur between?

Answer 11

Non metals.
In covalent bond, each atom donates valence electron to the bond, to share a pair electrons to fill outer shell to achieve noble gas structure.

Question 12

Why do covalent bonds differ in strength?

Answer 12

The strength is measured using average bond enthalpy.
Larger enthalpy, stronger the covalent bond.

Question 13

What exceptions to the octet rule do Be and B have in covalent bonding?

Answer 13

They don’t have enough unpaired electrons to reach noble gas configuration.
Can have less than 8 electrons in outermost level.

Question 14

What elements have expansions to the octet rule in covalent bonds?

Answer 14

P, As, S, Se, Te, Cl, Br, I, At
May result in more than 8 electrons in outer shell.

Question 15

What are the 3 bonds in covalent bonds?

Answer 15

Single covalent, double covalent and triple covalent.

Question 16

What are examples of giant covalent structures?

Answer 16

Diamond, graphite and graphene.
They are made of of many atoms bonded together by covalent bonds.

Question 17

Whats the structure and properties of diamond?

Answer 17

• giant covalent structure. Each carbon atom covalently bonded together 4 other carbon atoms in a tetrahedral shape. Held by strong covalent bonds.
• high mp as large amount energy needed to break covalent bonds.
• poor conductor electricity as no delocalised electrons.
• insoluble in water as covalent bond too strong to be broken by either polar/non polar solvents.

Question 18

What is the structure and properties of graphite?

Answer 18

-giant covalent structure. Each carbon atom covalently bonded together 3 other carbon atoms in trigonal shape. Graphites layered structure with delocalised electrons between layers.
- high mp, large amount energy needed break strong covalent bonds.
- good conductor electricity as electrons between layers are delocalised.
- insoluble in water as covalent bonds too strong to be broken by polar/non polar solvents.
- lubricant, layers can slide over each other as forces holding layers are weak.

Question 19

What are the properties of graphene?

Answer 19

-good electrical conductor as has delocalised electrons which are free to move and carry a charge. Without layers electrons can move much more quickly.
- high mp and bp, large amount energy needed break strong covalent bonds between atoms.
- single layer graphene is transparent and light.
Useful in touchscreens and aircraft technology as transparent and flexible.

Question 20

What are simple covalent structures?

Answer 20

Made up of molecules held together by weak induced dipole-dipole forces between the molecules. Atoms within molecules held by strong covalent bonds.

Question 21

What are the properties of simple covalent structures?

Answer 21

-low mp because little energy needed to break weak induced dipole-dipole forces between molecules.
- doesn’t conduct electricity as no free electrons
-

Question 22

What is the properties of the simple covalent structure of ice?

Answer 22

Atoms held by covalent bonds.
Molecules held by hydrogen bonds which are intermolecular forces.
In lattice of ice, hydrogen bonds hold molecules further apart than in water, ‘open lattice’
When ice melts, hydrogen bonds break and water molecules move closer together.

Question 23

What is dative bonding?

Answer 23

The sharing of a pair of electrons where both electrons in a bond are provided by one of the bonding atoms.

Question 24

What is metallic bonding?

Answer 24

The electrostatic forces of attraction between a lattice of + charged ions and a sea of delocalised electrons.

Question 25

How are giant metallic bonds formed?

Answer 25

Between metals, metal ion lose electron to become charged. + ions occupy fixed position in lattice. Electrons no longer belong to any one atom are free to move through structure so are delocalised.

Question 26

What are the properties of giant metallic bonding?

Answer 26

- high mp and bp, attraction between + ion and delocalised elctron very strong and high temps needed to break the metallic bonds - excellent conductor of electricity, delocalised electrons move freely throughout structure and carry charge

Question 27

What does the shape of a simple covalent molecule determined by?

Answer 27

Number and type of electron pairs in outer shell surrounding central atom.

Question 28

What is the electron pair repulsion theory?

Answer 28

- electron pairs — charged so repel each other. - electrons exist in pairs (lone and bonding pairs) - lone pair slightly more electron dense and repels more than a bonded pair.

Question 29

What would diagram of CH4 (simple covalent molecule) look like?

Answer 29

4 bonded and 0 lone pairs. Bonded pairs repel each other. Tetrahedral shape formed. Bond angle of 109.5’

Question 30

Whats the shape and angle pf Beryllium Chloride?

Answer 30

Linear 180’ 2 bonding, 0 lone pairs

Question 31

Whats the shape and angle of Boron Trifluoride?

Answer 31

Trigonal planar 120’ 3 bonding, 0 lone pairs

Question 32

Whats the shape and angle of an ammonium ion?

Answer 32

Tetrahedral 109.5 4 bonding 0 lone

Question 33

Whats the shape and angle of a sulfur hexafluoride (SF6) ?

Answer 33

Octahedral 90 6 bonding pairs 0 lone pairs

Question 34

What is the shape and angle of a ammonia?

Answer 34

Pyramidal 107 3 bonding pairs 1 lone pair

Question 35

Whats the shape and angle of water ?

Answer 35

Non linear 104.5 2 bonding pairs 2 lone pairs

Question 36

Why do lone pairs repel more than bonded pairs? (Electron pair repulsion theory)

Answer 36

Lone pairs more electron dense Lone pairs of electrons repel more than bonded pairs. Lone pairs push bonded pairs closer together.

Question 37

What is the sequence from highest to lowest repulsion using lone and bonded pairs?

Answer 37

Lone-lone , lone-bonded, bond-bond.

Question 38

Whats the definition of non polar?

Answer 38

In covalent bond When atoms are the same , the electrons are distributed equally directly between the 2 atoms ( e.g. H-H , F-F)

Question 39

Whats the definition of polar?

Answer 39

In covalent bond , Bond polar if electrons lie closer to 1 atom than the other so a permanent dipole if formed. (From a difference in the electronegativity) Between different atoms when one has a stronger attraction for the electrons than the other. (E.g. water.)

Question 40

What is electronegativity ?

Answer 40

The ability of an atom to attract a bonding pair of electrons in a covalent bond. The greater the difference in electronegativity, the greater the permanent dipole and the more polar the covalent bond

Question 41

What is a non polar molecule?

Answer 41

Symmetrical molecules non polar because dipoles can cancel each other out. E.g. each x-x bond is polar/non polar because of the difference in electronegativity between x and x. The dipoles in each bond cancel out because molecule is symmetrical. X is a non polar molecule as theres no overall dipole.

Question 42

What is a polar molecule?

Answer 42

Unsymmetrical molecules which contain 1 or more polar covalent bonds are polar as dipoles cannot cancel each other out. E.g. each x-x bond is polar cause of different in electronegativity between x and x. Dipoles in each bond cannot cancel each other out cause molecule is unsymmetrical. X is a polar molecule as theres a overall dipole.

Question 43

How is an induced dipole dipole ( intermolecular force) created?

Answer 43

Distribution of electrons in molecule/atom may be uneven. Uneven distribution of electrons in molecule/atom cause temporary dipole . Temporary dipole in 1 molecule/atom induces a dipole in neighbouring molecule as electrons repel each other. The d + of dipole attracts d- of dipole in neighbouring to produce induced dipole dipole force. The strength determined by number electrons in atom or molecule. As number electrons increase, bp increases as more energy needed to overcome strong induced dipole dipole forces.

Question 44

How are permanent dipole- permanent dipoles formed (intermolecular forces) ?

Answer 44

Between polar molecules. They are weak attractive forces between permanent dipoles in neighbouring molecules. E.g. X is a polar molecule because x is more electronegative than x . A intermolecular force, permanent dipole-permanent dipole force exist between 2 X molecules. The forces are stronger than induced dipole dipole.

Question 45

How are hydrogen bonds formed ?

Answer 45

Hydrogen bond is a strong dipole dipole interaction between molecules containing -OH ,-NH! Or -HF bonds. Hydrogen bonds are the strongest intermolecular forces. Form between a Hd+ atom in one molecule and a lone pair on a highly electronegative atom (Od-, Nd-,Fd-) on another.

Question 46

What are the anomalous properties of water due to the presence of hydrogen bonds between molecules?

Answer 46

-Ice is less dense than water as its an open lattice with hydrogen bonds holding the molecules further apart than in liquid state. -The hydrogen bonds lengthen when water freezes holding molecules further apart so theres more space between the molecules. -Water has a higher bp than expected. Hydrogen bonds between molecules have to be broken to boil. - hydrogen bonds are strong forces of intermolecular attraction so more energy than expected needed to break them.