Bonding Flashcards
What are ions?
Charged particles
What is the formula for an ammonium ion?
NH4-
What is the formula for a carbonate ion?
CO3,2-
What holds positive and negative ions together?
Electrostatic attraction
What are ionic crystals?
Giant lattices of ions
Describe the electrical conductivity of ionic compounds
- They conduct electricity when liquid as ions are free to move and carry charge
Do ionic compounds have high or low melting points?
High
Explain why ionic compounds have high melting points
Giant ionic lattices are held by strong electrostatic forces
Why are ionic compounds soluble in water?
Because of water’s polarity
How does water dissolve ionic compounds?
H2O molecules pull ions away from regular ionic lattice
What is a covalent bond?
A shared pair of electrons
Where is the attraction between in a covalent bond?
Between positive nuclei and shared pair of electrons
How are atoms held in simple covalent compounds?
With strong, covalent bonds
In simple covalent compounds, are there strong forces of attraction?
No, they are WEAK
Can simple covalent compounds conduct electricity?
No, they are insulators
Do simple covalent compounds have high or low melting/boiling points?
Low
Describe the general structure of macromolecular structures
Huge network of covalently bonded atoms
Describe the structure of graphite
- Carbon atoms arranged in sheets of a flat hexagons
- Carbon atoms form 3 other bonds, leaving delocalised electrons
What intermolecular force holds graphene sheets together?
Van der Waals
State 3 properties of graphite
- Slippery
- Conductors
- Low density
- High melting point
- Insoluble
Why is graphite slippery?
Weak intermolecular forces between layers allow layers to slide
Why can graphite conduct electricity?
- Delocalised electrons can move freely through structure
Why does graphite have a very low density?
- Graphene sheets are far apart compared to bond length
Explain why graphite has a high melting point
Strong covalent bonds within hexagon sheets
Why is graphite insoluble?
Covalent bonds are very hard to break
Describe the structure of diamond
- Carbon atoms covalently bonded to four other atoms
- Atoms arranged in tetrahedral crystal lattice
Give 3 properties of diamond
- High mp
- Very hard
- Thermal Conductors
- Insulator
- Insoluble
Explain why diamond is so hard
- Covalent bonds are very strong, there are lots of bonds
Why can diamond conduct heat?
Vibrations can travel easily through stiff lattice
Can diamond conduct electricity?
No, no delocalised electrons
What is a co-ordinate bond?
Where one atom provides both shared electrons
Give an example of an ion that contains a co-ordinate bond
Ammonium
What is a charge cloud?
An area where you are likely to find an electron
Why do charge clouds repel each other?
As electrons are all negatively charged
What type of charge clouds repel each other the most?
Lone Pair - Lone Pair
Which charge clouds produce the weakest force of repulsion?
Bonding pair - Bonding pair
State and explain the bond angles in a molecule with a linear shape
- 180*: Charge clouds repel so they are as far away as possible
What shape is a molecule with 3 bonding pairs?
Trigonal Planar
What are the bond angles within a ‘bent’ molecule?
120*
Explain why a ‘bent’ molecule is different to a linear-shaped molecule
Lone pair - Bonding pair repulsion is stronger than bonding - bonding pair repulsion
Why are all bond angles the same within an ammonium ion?
4 bonding pairs all repel each other equally
What is the shape of a methane molecule?
Tetrahedral
What are the bond angles within a tetrahedral-shaped molecule?
109.5*
What shape is a molecule of ammonia?
Trigonal Pyramidal
Explain why ammonia has a trigonal pyramidal shape
Lone pair on Nitrogen repels bonding pairs more pushes bonding pairs closer together. 107*
How many bonding pairs are there in a ‘bent’ molecule?
2 bonding pairs
Give an example of a bent-shaped molecule
Water
What shape is a molecule with only 5 bonding pairs?
Trigonal Bipyramidal. 90, 120
How many bonding and lone pairs are there in a molecule with a ‘see-saw’ shape?
4 bonding pairs, 1 lone pair
How many bonding and lone pairs are there in a ‘T-shaped’ molecule?
3 bonding pairs, 2 lone pairs
Give the shape of a molecule with only six bonding pairs
Octahedral. 90*
What are the bond angles within a ‘T-shaped’ molecule?
87.5*
What are the bond angles in any molecule with six electron pairs overall?
90*
What is the shape of a molecule with 5 bonding pairs and 1 lone pair?
Square Pyramidal
How many bonding and lone pairs does a molecule with a ‘square-planar’ shape have?
4 bonding pairs, 2 lone pairs
What is electronegativity?
The ability to attract bonding electrons in a covalent bond
What are the top 3 most electronegative atoms?
Cl, O, F
Why are covalent bonds in diatomic gases non-polar?
- Atoms are the same and have equal electronegativities
- Electrons are equally attracted to both nuclei
What occurs to bonding electrons in a polar bond?
Bonding electrons are pulled towards the more electronegative atom
What causes a dipole in polar bonds?
The difference in electronegativities
What is a dipole?
A difference in charge caused by a shift in electron density within a bond
What is a permanent dipole?
A dipole that forms when charge is distributed unevenly
What type of dipole do polar molecules have?
Permanent dipole
What kind of dipole does HCl have and why?
- The polar bond is distributed unevenly
- Permanent dipole
Why isn’t methane a polar molecule?
The dipoles cancel each other out as methane is symmetrical
Do larger molecules have stronger or weaker VdW’s?
Stronger, as larger electron clouds
State the 3 types of intermolecular forces
- Van der Waals
- Permanent dipole-dipole
- Hydrogen bonding
What intermolecular force is present in all molecules and atoms?
VdW
Explain how a temporary dipole is formed
At any moment, electrons are more likely to be on one side of an atom than another
Do long straight molecules have stronger or weaker VdW’s than branched molecules?
Stronger, as molecules can lie closer
What are permanent dipole-dipoles?
Weak electrostatic forces of attraction between D+ and D- charges
Why would a charged rod cause polar liquid to move towards it?
Polar molecules can turn so oppositely charged atoms can move towards the rod
What is the strongest intermolecular force?
Hydrogen bonding
Which three elements create hydrogen bonding when bonded to hydrogen?
Fluorine
Nitrogen
Oxygen
Why does F-H, N-H and O-H bonds create hydrogen bonding?
As F/N/O are very electronegative
Explain how hydrogen bonding works within an O-H bond
- O-H bond is very polar
- Hydrogen has high charge density
- H atoms form weak bonds with lone pairs on O
Describe bonding and intermolecular forces within simple, covalent structures
- Strong covalent bonds
- Weak intermolecular forces
Are simple, covalent structures good electrical conductors?
No, as no free ions or electrons to carry charge
Describe melting points in simple, covalent structures
Low mp. due to weak intermolecular forces
Describe metallic bonding
The electrostatic attractions between delocalised e- and positive metal ions
Explain why metals have high melting points
Strong electrostatic attraction between positive ions and delocalised electrons
Why are metals malleable?
No bonds between ions so layers can slide over each other
Explain why metals are good conductors of heat
Delocalised electrons can pass kinetic energy
Why aren’t metals soluble as solids?
Very strong metallic bonds
What state are giant covalent structures at room temperature?
Solid
What state allows ionic compounds to conduct electricity?
Liquid, ions are free to move
Do simple covalent structures have high or low mp/bp?
Low melting and boiling points
