Bonding And Structure Part 1 Flashcards
Why are the noble gases inert?
They have a full outer shell of electrons so are stable
Describe what the octet rule states
All atoms, except the noble gases, will react with other elements to gain a full outer shell
What is meant by an ionic bond? (2)
A strong electrostatic force of attraction between oppositely charged ions
(usually consists of a non-metal and a metal)
What is meant by a covalent bond? (2)
A strong electrostatic force of attraction held between a shared pair of electrons and the nuclei of the bonded atoms
(compounds of non-metals)
What is meant by a metallic bond? (2)
A strong electrostatic force of attraction held between a lattice of positive metal ions and a sea of delocalised electrons
Draw a dot and cross diagram to show the bonding in Li2O
2[Li]+ + [O]2-
no electrons shown on lithium and electrons shown clockwise on oxygen as xxxxxoxo
Draw a dot and cross diagram to show the bonding in MgCl2
[Mg]2+ + 2[Cl]-
No electrons shown on Mg and electrons shown clockwise in Cl as xxxxxxox
Draw a dot and cross diagram to show the bonding in Na3P
3[Na]+ + [P]3-
No electrons shown on Na and electrons shown on P clockwise as xxxoxoxo (as p sub shell fills each orbital separately)
Name the 4 types of structure in bonding
Giant Ionic lattice
Giant Metallic lattice
Simple covalent
Giant covalent (macromolecular)
State two examples of macromolecular crystals
Graphite
Diamond
Explain why diamond has a high melting point (3)
Each carbon atom forms 4 covalent bonds, giving it a very strong 3D structure, so is a very hard material
Explain why graphite is slippery (3)
Consists of layers of carbon atoms which each form 3 covalent bonds, which allows for a free delocalised electron. This means separate layers are held together by weak London forces, so the layers can slide
Describe what is meant by the term ionic lattice (2)
Oppositely charged ions held together by electrostatic forces of attraction, in a regular and repeating pattern
What do some group 6 elements do? (2)
Either keep their 6 electrons, or have more than 6 (e.g sulfur has 12 in sulfur hexafluoride)
What is meant by a dative covalent bond? (1)
Where only one of the atoms supplies both of the elections shared in a covalent bond
Draw a dot and cross diagram to show bonding in NH4
3 hydrogens bonded normally with N, 1 hydrogen receives a dative bond from N, overall + charge
What can be drawn to represent a dative bond? (1)
An arrow pointing from the donor to the receiver
E.g N->H in NH4
What bonds is a carbon monoxide molecule held together by?
2 normal bonds (4e-) and a dative bond from oxygen to carbon
What are the 4 rules in deciding the shape of a molecule?
- Electron pairs repel each other as far apart as possible- lone pairs decrease the bond angle by 2.5 degrees
- Lone pairs repel more strongly than bonding pairs
- Shape is determined by the number and type of electron pairs (bond/lone) around the central atom
- Double bonds class as 1 bonding region, not 2 (bonding regions are what determines shape)
What is the shape and bond angle in beryllium chloride, BeCl2? (2) How many bonding and lone pairs of electrons? (1)
Linear 180 degrees
2 bonding pairs and 0 lone pairs
What is the shape and bond angle in Boron triofluoride, BF3? (2) how many bonding and lone pairs of electrons are there? (1)
Trigonal planar- 120 degrees
3 bond pairs, 0 lone pairs
What is the shape and bond angle in ammonium? (2) how many bonding and lone pairs of electrons are there? (1)
Tetrahedral- 109.5 degrees
4 bond pairs, 0 lone pairs
(1 dative bond)
What do dotted wedges, solid lines and filled wedges mean?
• A solid line represents a bond in the plane of the paper
• A dotted wedge goes into the plane of the paper
•. A filled wedge comes out of the plane of the paper
In ammonium, going clockwise, which bonds are shown to be bonded to the hydrogen? What additional things to remember?
Solid, dotted, filled, solid
Dotted line faced slightly above 90 degrees (from top H)
Filled line slightly less than 180 degrees (clockwise from top H)
One solid line facing directly up, another at 90 degrees to the filled wedge
What is the shape and bond angle of a compound with 6 bond pairs? (2)
Octahedral, 90 degrees
In sulfur hexafluoride, state what bond is where, in a clockwise motion
Top F solid line, then dotted, filled, solid, filled, dotted
What is the shape and bond angle in carbon dioxide? (2) Why? (2)
• Linear
• 180 degrees
• 2 bonding regions, with 4 bond pairs which repel each other as far apart as possible, no lone pairs
What is the shape and bond angle in CO2, and why? (4)
- Linear
- 180 degrees
- 2 bonding regions, with 4 bond pairs which repel each other as far apart as possible, no lone pairs
What is the shape and bond angle in ammonia? (2) why? (3)
• Pyramidal
• 107 degrees
• Around the central N atom there are 3 bonding pairs and 1 lone pair of electrons which repels more than the bonding pairs
• Each electron pair takes 2.5 degrees away, so 109.5-2.5=107, as 4 electron pairs= originally tetrahedral structure
What is the shape and bond angle in water? (2) why? (3)
• Non-linear
• 104.5 degrees
• 4 electron pairs so initially 109.5 bond angle, but the two lone pairs around O repel more than the two bonding pairs of electrons so repulsion no longer equal
Explain the trend in boiling point when charges of ionic compounds increases, e.g NaCl to MgO (3)
Boiling point increases as the electrostatic attraction between the delocalised electrons and the positively charged ions increases, so requires more energy to overcome
Summarise the properties of most ionic compounds
• Soluble in polar substances such as water
• High melting and boiling points
• Only conduct electricity when molten or aqueous as ions free to move and carry the charge
Define the term average bond enthalpy
The amount of energy required to break one mole of bonds between two atoms in gaseous state
If asked to draw the dot and cross diagram for charged polyatomic ions like carbonate, what is to remember?
Oxygen gained electrons from a metal- giving it a negative charge
•so display this electron as a different shape to the others
Bond angle in COOH?
120 degrees- 3 bonding regions around C, no lone pairs
