Chemical Bonding Part 2 Flashcards
When the covalent bond is polar? (2)
The molecule is either polar or non polar
What determines whether it is polar or non polar? (1)
Shape of the molecule
What is the polarity of a molecule? (1)
- Sum of all bond polarities
If the diatomic molecule is polar…
There will be what? (1)
An Electronegativity difference
If the molecule is not diatomic…
What can tell you the molecule is polar or non polar? (1)
The shape of the molecule
Properties of:
WATER - H2O (4)
- Angular
- Therefore not symmetrical (no sides cancel)
- H-O bond polar covalent
- Therefore polar molecule
Properties of:
AMMONIA - NH3 (4)
- Pyramidal
- Therefore not symmetrical
- N-H bond polar covalent
- Therefore molecule is polar
Properties of:
CARBON DIOXIDE - CO2 (4)
- Linear shape
- Symmetrical (bonds cancel)
- Therefore molecule is non polar
- C-O bond polar covalent
Properties of:
SULPHUR DIOXIDE - SO4 (4)
- Bent shape
- Therefore not symmetrical (sides don’t cancel)
- S-O bond polar covalent
- Therefore polar molecule
Properties of:
METHANE - CH4 (4)
- Tetrahedral
- Symmetrical (bonds cancel)
- Therefore molecule is non polar
- C-H bond polar covalent
Properties of:
CARBON TETRACHLORIDE - CCl4 (4)
- Tetrahedral
- Symmetrical (bonds cancel)
- Therefore molecule is non polar
- C-Cl bond polar covalent
All halogens will give what? (2)
- A symmetrical molecule
- Therefore non polar molecule
Is oil polar or non polar? (1)
Non polar
What is an Intramolecular force? (2)
- Intramolecular forces are forces inside the molecule keeping compounds together
- Namely in covalent bonding
What is an Intermolecular force (2)
An intermolecular force is a weak force of attraction between molecules or between atoms of noble gas
Intra & Inter
WATER
(3x3)
Intramolecular
- H-O attraction
- X25 strong than Inter
- 464 KJ/mol to break down
Intermolecular
- H2O to H2O attraction
- Not as strong as Intra
- 19 KJ/mol to break down
What is the breaking down of molecular forces known as? (1)
Sublimation
Give 4 examples of what strength influences in a molecule? (4)
- Shape
- Volume
- Surface Tension
- Ability to flow
- Rate of evaporation
- Melting and boiling points
The stronger the intermolecular force… (2)
The greater the amount of energy needed to move molecules apart
Van Der Waals forces are weaker than… (2)
- Chemical bonds
Lower melting points - Intramolecular forces
Noble gases do not…? (2)
- Bond with other elements
- Held together by London Forces
Dipole - Dipole? (3)
- Positive and Negative poles in the molecule
- Weaker than Ionic and Metallic
- Molecules must be almost touching or touching
Example of Dipole - Dipole? (3)
HCl
- Attraction relatively weak
- Cl-H X130 more strong than HCl–HCl
- Boiling point is -85°C
Dipole - Induced Dipole? (3)
- Created by disturbing the arrangement of the electrons
- weaker than dipole - dipole
- Stronger than London forces
Example of Dipole - Induced Dipole? (2)
H-Cl – Ar
- H-Cl is dipolar
- Ar is non polar
- dipole induces a temporary dipole in Argon
Which non polar gases create a Dipole - Induced Dipole molecule? (2)
O2 & CO2
- Dissolve sparingly into water
Different names for London Forces (3$
- Momentary Dipole Forces
- Induced Dipole - Induced Dipole
- Dispersion Forces
London Forces? (3)
- Weakest of the Van Der Waals Forces
- Temporary attractive force
- Causes non polar substances to
:: condense into liquids and
:: freeze into solids when the temperature is lowered
London forces exist between? (2)
- 2 Non Polar Molecules
- Atoms of noble gases
The bigger the molecule… (2)
Intermolecular
- Heavier
- Stronger the forces
The bigger the atom… (2)
- The further the valence electrons are from the nuclei
- Still strong enough forces to be SOLID or LIQUID at room temperature
The attraction between Helium atoms. (4)
- Helium liquid at room temperature below 4K
- Forces of attraction between neutral atoms, increases as atoms get closer
- Helium atom is perfectly symmetrical
- BUT movement of the electrons around the NUCLEI can cause electron distribution = A momentary dipole
Van Der Waals strength determined by… (2)
- Number of electrons (size of electron cloud) surrounding the molecule which increases with molecular mass
- The surface area (size) of the molecule
Larger the molecule… (2)
Smaller the molecule… (2)
- Easier it is to redistribute and form
- Easier polarized
- Harder to polarize
- Electrons close to the nucleus
Overtime non polar molecules have…? (1)
However…? (2)
- Symmetrical distribution of electrons
- There is a probability that the electron density has shifted
- Creates a brief POLARIZATION of charge or a TEMPORARY DIPOLE
The strength of the Van Der Waal forces determines…? (2)
- How easily the electron cloud can be polarized
- MOLECULAR MASS + , INTERMOLECULAR FORCE +
5 point on Intermolecular forces and molecules (5)
- Bigger molecules = bigger electron clouds
- Makes them more easily polarized
- Form stronger dipoles
- Therefore stronger intermolecular forces
- Takes more energy to break the stronger bond
CH4 compared to C2H6?
Stronger? Bigger? Etc. (4)
C2H6
- Stronger
- Molecule is bigger
- Higher boiling point
- More energy required to overcome force of attraction
When the covalent bond is non polar (1)
The molecule is non polar
What is a Hydrogen bonding is very polar, why? (6)
- An attractive force between a hydrogen atom and a covalently bonded small, very electronegative atom such as
- N, O, F
- Top groups of 5:6:7
- Electrons spend a lot of time around these elements.
- Therefore hydrogen nucleus exposed = Substantial
NH3, H2O, H-F
Why is Water not a gas at room temperature? (2)
- Abnormally high boiling point
- Small molecule weight
Capital Delta shows? (1)
Strong forces
Hydrogen bonded with Water is responsible for… (3)
- High surface tension
- Heat of evaporation high
- Solid phase less dense than liquid phase
Hydrogen compared to covalent? (1)
1/10 the strength
Hydrogen bonding responsible for… (3)
- Genes in the DNA molecule
- Hylical structure of protein
- incredible strength of KEVLAR (Canoe hulls & bullet proof vests)
Why does H2O have a higher boiling point thank H2S?
Same hydrides of group 6? (2)
- H2O involves hydrogen bonding
- Very strong bond, require more energy to break than H2S
- Therefore higher boiling point
Explain why H2S has a higher boiling point than H2Se? (5)
- H2Se is a bigger molecule
- Electron clouds more easily polarized
- Stronger intermolecular forces
- Therefore more energy required to break the bond
- Therefore higher boiling point
Non metals are… than metals (1)
More electronegative
What happens during Ionic bonding? (5)
- Difference greater than 2,1 in Electronegativity
- Between metal and a non metal
- Non metal pulls electrons so strongly they completely leave the metal
- 2 oppositely charged Ions - Coulombic charges
- Held together by ELECTROSTATIC RADIATION
Ionic bonding forms? (2)
- Salts
- Ionic substances
When does Ionic bonding occur? (5)
- When non metals bond with metals
- Metal loses electrons, becomes + ion (cation)
- Non metal gains electrons, becomes - ion (anion)
- 2 ions attract each other by an Electrostatic force
- Ions pack together in a crystal lattice
What is an Ionic bond? (2)
An Ionic bond forms due o the transfer of electrons and subsequent electrostatic attraction
What is a crystal lattice? (2)
A crystal lattice is a regular three-dimensional structure of particles
What is a Metallic bond? (2)
A metallic bond is between a positive kernel and a sea of de localized electrons
What do metals tend to have? (1-5)
High Melting & Boiling Point - Therefore forms strong bonds - High in density \: electrons packed close together \: Outer orbitals overlap \: Valence electrons become DELOCALIZED
Metals are held together by… (2)
Strong forces of attraction between
+ Nuclei
- delocalized electrons
Why can metals conduct a current? (2)
- Sea of delocalized electrons
- That can move
Ion - Dipole? (4)
- Attractive force
- Electrostatic attraction
# Ionic compounds in Polar Liquids
NaCl in H2O
Ion - Induced Dipole (4)
- Weak attraction
- By disturbing the arrangement of the electrons in Non Polar
# Ionic compounds in Non Polar Liquids
Fe and O2
Simple small molecule has… (1)
Give 4 examples? (4)
- Few atoms
- O2 Oxygen
- H2O Water
- C18H18 Petrol
- C12H22O11 Sugar
A giant molecule has… (1)
Also known as… (1)
Examples? (4)
- Millions of atoms per molecule
- Macromolecule
- Diamond, Graphite, Silicon Dioxide, Sodium Chloride
Giant molecules are. (3)
- Some of the hardest structures known
- Strong bonds between their atoms
- High melting & boiling points
What are Allotropes? (4)
- Different forms of the same element
- Different bonding arrangements between atoms
- Result in different structures w/ chemical and physical properties
- Diamond, Graphite & Charcoal : Allotropes of Carbon
Diamond? (6)
- Single giant molecule
- Made up of endless strong covalent bonds between C atom
- Each C atom covalently bonded to 4 other C atoms
- Why it is the hardest natural substance
- Very high melting point : 3550°C
- No free electrons : Excellent insulator
Graphite? (6)
- Made up of carbon atoms
- Each C atom valency bonded to 3 other C atoms
- Link up, form 6 membered rings : form planes U flat sheets of C
- 4th electron of each carbon : not bonded : becomes delocalized
- Delocalized electrons can conduct an electric current
- Used to make electrodes (during electrolysis)
Planes and Flat Sheets in Graphite? (7)
- Covalent bonding between C atoms in planes is : STRONG
- Flat sheets of C lie on top of each other
- Held together by weak forces of attraction (London)
- Spacing between bigger than diameter of the individual atom
- Forces weak : sheets easily slide past each other
- Sliding sheets give graphite its softness
- for Writing and Lubricating properties
Sodium Chloride? (2)
- Giant molecule
- Ionic bonding
SOLID Sodium Chloride? (4)
- Ions held very close together
- With very strong forces
- Are unable to move apart
- Therefore cannot conduct and electric current (NaCl)
Solid NaCl added to Water? (5)
- Ions can separate : Dissociate
- Move freely throughout water
- Ions become surrounded by polar water molecules
- ION - DIPOLE force of attraction
- Aqueous solution = Conducts an electric current
Molten NaCl? (2)
- Ions able to move
- Conducts electricity in a liquid phase
For a substance to conduct an electric current ? (2)
- Charged particles must be able to move
- Charged particles can be +, -, or - ions
Silicon Dioxide? (7)
- Giant covalent molecule
- Each Si-O bond is a single bond
- Each Si bonds with 4 Oxygen Atoms
High melting point : 1700°C : Si-O bonds must be broken before melting
Hard
Doesn’t conduct electricity : No delocalized electrons
Insoluble in : water and organic solvents
Ionic solids don’t conduct but Ionic liquids do? (2)
Liquids have a charge that’s free to move
Solids are locked in the crystal
Ions flow in liquid not in a fixed position
Electric currents created by delocalized electrons
Solutions of Ionic solids don’t conduct an electric current?
No delocalized electrons?
