Chemical Bonding and Structure Flashcards
What type of state are Ionic Substances in-room Temperature?
Solids
Why is the Melting and Boiling Point of Magnesium Oxide higher than Sodium Chloride?
The electrostatic attractions between 2+ and 2- ions in the Magnesium Oxide are stronger than those between the 1+ and 1-
Higher Temp is required to provide sufficient energy to separate the ions in Magnesium Oxide
The force of the ions between ions is proportional to the product of the charges (whilst all other things being equal)
How Volatile are Ionic Compounds?
Low Volatility (refers to how readily a substance evaporates)
THIS IS BECAUSE THE ELECTROSTATIC FORCES OF ATTRACTION BETWEEN THE IONS ARE STRONG
How Soluble are Ionic Compounds in Water?
Often Soluble in Water
Water is a polar solvent, and energy is released when the ions are hydrated by being surrounded by water molecules
This energy pays back the energy required to break apart the ionic lattice
How Soluble are Ionic Compounds in Non-Polar Solvents?
Not usually Soluble (hexane)
A great Deal of Energy is required to break apart the ionic lattice
This is not paid back by the energy released when the non-polar solvent forms interactions with the ions
Electronegativity?
measure of the attraction of an atom in a molecule
for the electron pair
in the covalent bond of which it is a part
What is the rule of Electronegativity?
In a covalent bond between two different atoms, the atoms do not attract the electron pair in the bond equally
This is because of the size of the individual atoms and their nuclear charge
What does it mean if an Element is more electronegative than the other in an ionic compound?
Let’s take a cheeky lil example:
HF, Fluorine is more electronegative than hydrogen
Thus, F attracts the electrons in the H-F bond more strongly than hydrogen atom does.
Do Noble Gases have electronegativity values?
No, since they don’t form compounds
How does electronegativity compare between Non-Metals and Metals?
Non-Metals have higher electronegativities than metals
What is a Coordinate Covalent Bond?
A Coordinate Covalent bond is a type of covalent bond in which both electrons come from the same atom.
Carbon Monoxide in Covalent Bonding?
Pg 131
Resonance Structures?
Pg 133
How can we predict the shapes of molecules?
VESPR THEORY
VESPR Abbreviation?
Pairs of electrons (electron domains) in the valence (outer) shell of an atom repel each other and will therefore take up positions in space to minimise these repulsions - to be as far apart in space as possible.
What does the shape of a molecule depend on?
Number of Electron Pairs
What is the difference between the black triangle bond symbol and the dashes triangle bond symbol?
Page 138
What is the order of Repulsion Strength for pairs of electrons?
Lone Pair - Lone Pair –>
Lone Pair - Bonding Pair –>
Bonding Pair - Bonding Pair
Why are the Lone Pair Lone Pair repulsion strengths stronger?
Lone Pairs are held closer to the central nucleus than bonding pairs
Lone Pairs are closer to the bonding pairs of the electrons
than the bonding pairs are to each other
And repel them more strongly
Repulsion due to lone pairs causes other bond angles to become smaller
Examples of Molecules that use lone pairs?
NH3 (1 pair)
H20 (2 Pairs)
How to distinguish between Polar and Non-Polar Molecules?
If it’s a Hydrocarbon its Non-Polar
If the molecule has symmetry, it’s non-polar
Polar Molecules have an electronegativity of more than 0.5
Just because a symmetrical molecule is nonpolar doesn’t mean its polar –> Depends on the electronegativity difference
If Hydrogen is attached to N, O or F it’s polar
S-O-F rule?
Although S-C is 0 EM
C-O is 1 EM
Therefore, it’s polar
Why are Molecules of Symmetry non-polar?
The symmetry of the molecules causes the individual dipole moments of the bonds to cancel out.
What is meant by Basic Shape?
The arrangement of the electron pairs around the central atom
Silicon Dioxide bond, shape?
- Giant Covalent Structure
- Each Silicon atom is bonded to 4 Oxygen atoms in a tetrahedral array
- Each O bonded to 2 Si Atoms
- Due to Lone pairs on each Oxygen Atom, the basic shape about each Si-O-Si is bent
Characteristics of C60 (Buckminsterfullerene)?
Insoluble in Water but soluble in some organic solvents such as benzene
The energy to overcome the London forces between C60 molecules us paid back by the energy released when London forces are formed between the C60 and the Solvent
Can’t conduct electricity
Although C forms 3 bonds in the C60 molecule, the molecular structure means that the electrons are not able to move from one molecule to the next
What types of Intermolecular forces are there?
LDF
Dipole-Dipole Interactions
H-Bonding
The strength of the London(dispersion) forces in between molecules depend on two factors
the number of electrons in the molecule
Surface area of the molecules
How does the Number of Electrons affect the strength of LDF?
The greater the number of electrons in a molecule, the greater the likelihood of a distortion and thus the greater the frequency and magnitude of the temporary dipoles
The dispersion forces between the molecules are stronger and the melting and boiling points are larger
How does SA affect the strength of LDF?
The larger the surface area of a molecule, the more contact it will have with adjacent molecules
The greater its ability to induce a dipole in an adjacent molecule, the greater the London (dispersion) forces and the higher the melting and boiling points
Structure and Bonding of Graphite?
- Arranged in Layers
- C atoms within each layer are connected by 3 Covalent Bonds
- Weak Intermolecular Forces
Why is Graphene Soft?
Weak intermolecular forces between the layers
Layers can slide over each other
What are the Intramolecular forces like in the bonding HCN?
Electrostatic attractions between pairs of electrons and positively charged nuclei
What occurs in Hydrogen Bonding?
The electronegative atom withdraws electron density from the hydrogen, polarising the bond such that there is a strong interaction between delta + and delta - on the other molecule
Are Covalent Bonds broken during Melting and boiling?
No, only intermolecular forces
Arrange Sulfur, Chlorine in order of increasing boiling point and explain
They are all non-polar and therefore only intermolecular forces are London forces
Thus, the differences between them is due to the strength of the London forces which is affected by the relative molecular mas
The reasoning for A higher Temperature and Boiling Point?
The stronger the intermolecular forces, the more energy must be supplied to break them
and the higher the boiling points
how do intermolecular forces affect solubillity?
Generally, a substance will dissolve in a solvent if the intermolecular forces in the solute and the solvent are similar
Why does Sodium have a lower melting point than Magnesium
Magnesium has a higher melting point because magnesium ions are Mg2+ and sodium is Na+. Magnesium ions have a stronger positive charge so the attraction to the delocalised electrons is stronger. There are also more delocalised electrons in magnesium than there is in sodium.
Geometric Shapes?
See Google Image
Magnesium is a lightweight metal used for the manufacturing of car seats
Describe the structure and bonding present in Magnesium?
A regular lattice arrangement of metal ions
Surrounded by a sea of delocalised electrons
Electrostatic Attraction between the positive ions and delocalised electrons
Explain, with reference to bonding, the principal property of a metal that makes it suited to manufacturing shaped objects such as railings?
Metals are malleable
As the layers of positive ions can slide over each other
Because the positive ions are attracted to the sea of the delocalised electrons in all directions
Based on the type of intermolecular forces, explain the difference in solubility in water between ethane and ethanol
Ethane is soluble
Ethane has no polar bonds
Ethanol is soluble
Due to the Hydrogen bonding between the alcohol group and the water
State one property of Ionic Bonding and the nature of the Bonding?
Property - Brittle, High Melting Point and Low Volatillity
Nature - SEFOA
Electronegativity?
Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons toward itself.
Explain whether Hydrazine and ethene were polar or non-polar?
Ethene is non-polar
There is no net dipole moment in the molecule
Which Molecules have Resonance Structures?
It has to have more than one double bond
There must be one possible position to put the double bond as well
Which following structures don’t obey the octet rule?
BeCl2
BF3
H2O
What kind of bonding i s metallic bonding?
Non-Directional Bonding
Hydrogen Bonding?
N, O, F
Order of Electronic Configuration?
Diagram:
