Chemical Bonding and Structure Flashcards
What is metallic bonding
Is the electrostatic forces of attraction between metal cations and a sea of delocalised electrons
What are the 5 properties of metals
- conduct electricity
- malleable
- ductile
- high melting and boiling temperatures,
- good thermal conductors
What effects the ability of metals to conduct electricity and melting point
The more delocalised electrons there are the better they conduct electricity and the higher the melting point
What is ionic bonding
•Is the electrostatic forces of attraction between oppositely charged ions
The strength of ionic bonding depends on
What has this got to do with charge density
The bigger the charge on the ion, the stronger the electrostaic forces between ion
The smaller the ion, the stronger the electrostattic attraction between ions, as they can pack together more tightly
Having a small ion and large charge, will lead to a high charge density
Does ionic radii, increase or decrease down a group
•Ionic radii increases down group
Due to the addition of electron shells, so ionic radii increases
What are the 3 main properties of ionic compounds
high relatively high melting temperatures due to strong electrostaitc forces
can conduct electricity when molten or in aqueous solutions due to ions being able to move around
brittle, as layers can slide
Dissolve in water, as water molcules are polar, and attract the negative and positive ions
Are ionic compounds soluable in water
and why
- Ionic compounds are soluble in water because the positive ions will separate and becomes surrounded by electronegative oxygen molecules forming and ion-dipoles interaction.
- Negative ions will be removed from the lattice and become surrounded by hydrogen molecules forming hydrogen bonds.
- The energy for this is supplied by hydration energy
Evidence for ionic compounds can be found where
via electrolysis where the ionic molecules is dissolved in water and the positive ions will move toward the anion and the negative ions move towards the cation
What is covelent bonding
Is the electrostatic forces of attraction between nuclei of two atoms and the bonding pairs of electrons
How are covelent bonds formed
formed the overlap out their outer shell orbitals containing a single electrons
The area of overlap 2S orbitals is called
a sigma bond
The area of overlap in 2P orbitals is called a
Sigma bond
The area of overlap sideways between two P orbitals is called
Pi bond
A pi bond results in a what in a covalent bond
high electron density above and below the molecule
Bond length is
Is the distance between two nuclei of the two atoms covalently bonded
Bond strength is determined by
the amount of energy required to break a mole of bonds in gaseous state
The stronger the bond, the longer or shorter the length ?
•The stronger the bond the shorter the length
Nuclei with increased what, will have a greater bond strength
electrostatic attraction
What is electronegativity
•Is the ability of an atom to attract a bonding pair of electrons
What is the trend in electronegativity down a group and across a period
•This decreases down a group and increases across a period
Do molecules of the same element have the same or different distribution of electron density?
•Molecules of the same element have the same distribution of electron density
What is a polar covelent bond
•Polar covalent bonds is where there is a unsymmetrical distribution in electron density, due to a covalent bond with one atom carrying a slightly negative change and the other one positive
A polar covalent bond, is a covalent bond with a degree of
ionic character
What is a discrete molecule
- Is an electrically neutral group of two or more atoms held together by chemical bonds
- This means that the central atom does not have to have a full outer shell of electrons when covalently bonded
What is a dative covalent bond
- Is formed when an empty orbital of one atoms overlaps with an orbital containing a non bonded pair of electrons
- Represented by an arrow
What are the 3 rules of electron repulsion theory
- The shape of a molecules is cased by repulsion between pairs of electrons both bonded and non bonded
- Electrons surrounds themselves around the central atom where repulsion is at a minimum
- Lone pair – lone pair> lone pair – bonded pair> bonded pair – boned pair
Name the bond name and angle of a molecule with
2 bonds
0 lone pairs
linear molecules
180 degrees
Name the bond name and angle of a molecule with
2 Bonds
2 Lone pairs
V-shaped
104.5 degrees
Name the bond name and angle of a molecule with
3 Bonds
0 Lone Pairs
trigonal planar
120 degrees
Name the bond name and angle of a molecule with
3 Bonded pairs
1 lone pair
trigonal pyramidal
107.5
Name the bond name and angle of a molecule with
3 Bonds
2 Lone pairs
trigonal bipyramidal =
104.5
Name the bond name and angle of a molecule with
4 Bonds
0 Lone pairs
tetrahedral
109.5
Name the bond name and angle of a molecule with
6 Bonded pairs
0 Lone pairs
Octagonal
90 and 180 degrees
What is a polar molecule
•Polar molecules are molecules which have an unsymmetrical distribution of electron density caused by dipoles reinforcing another
Explain how an instantaneous dipole is formed
- If molecules possess a permanent dipole, will also interact with one another, and when aligned correctly there will be a favourable interaction and attract another.
- However random movement of atoms mean they are not always aligned
When does a hydrogen bond occur
•When hydrogen is bonded with a more electronegative atom than itself like oxgen, nitrogen and fluorine
What groups will form hydrogen bonds
•All compounds containing –O-H group
What are the hydrogen bonds in water described as
•Interaction is of an extreme dipole-dipole interaction and utilising lone pair on oxygen atom
The bond angle in water is
•Bond angle has to be 180 degrees
Two main features of water due to hydrogen bonding
a very high boiling temperature
low density as a solid than liquid
Why will water have a higher boiling point than other molecules with hydrogen bonds
•Water forms two hydrogen bonds per molecule so hydrogen bonding more extensive, hence high boiling temp
Why is the density of ice less than of liquid water
•When frozen, ice is arranged in 6 rings, held together by hydrogen bonds, which creates a large area open space
Why does boiling temperture increase with chain length in alkanes
- More electrons per mole so London forces will be stronger
- As the chain length increases there will be more point of contact, meaning and London forces between chains too
Why do alcohols have higher boiling points that alkanes
And how can we test this
- Alcohols also have hydrogen bonding which increases boiling tempertures
- Enthalpy change of vaporisation direct measure of intermolecular interactions, you can use it to work out the predominate bonding in alcohols
Why are alcohols soluable in water
•These Hydrogen bonds can form with water
What is the trend in solubility as chain length increases
solubility of alcohols decreases with increasing hydrocarbon chain length as London force becomes predominant
What is the trend with boiling point in halogen haildes
•Increase in HF then decreases to HCl and then continues with a steady increase with HBr and HI
Why from HCl to HI will there be a steady increase in boiling points
•The steady increase from HCL to HI due to the increasing amount of electrons which increases London forces
Why is HF boiling point extraodinarily high compared to other halogen halides
•HF has a very high boiling temp due to F having the highest electronegativity which effects the strength of hydrogen bonds
In order for a substance to dissolve
Solute particles must be separated from another and come surrounded by solvent particles
Forces of attraction between solute-solvent particle must be strong enough to overcome solvent-solvent solute-solute forces
How would you find a solvent for a non-polar molecule
If you’re searching for solvent for non-polar substance that has substantial non polar parts
then liquid that contains similar molecules is the answer
what are th 4 types of soild lattices
•Giant metallic, giant ionic, giant covalent, discrete molecular lattice
What are the four types of giant covalent lattices
Dimond, Graphite, graphene, fullerene
Describe the bonding in dimond
each carbon contains 4 sigma bonds to 4 other carbons, in a tetrahedral arrangement
Very hard due to the double carbon- carbon bonds
Describe the bonding the Graphite
Each carbon bonded to three other sigma bonds, forming hexagonal rings.
It has a deloclised electron in the p orbital.
It is a solid lubricant due to absorbed gases.
London forces between layers
Decribe the bonding and melting/tempertures in Molecular solids (fullerene)
low melting and boiling temperatures, as not breaking the covalent bonds,
bigger macro molecules have more electrons so higher London forces
•Intermolecular interaction are relatively stonger or weaker than electrostatic forces of attraction?
•Intermolecular interaction are relatively weaker than electrostatic forces of attraction
What creates instaneous dipole-dipole interactions
•London Forces create instantaneous dipole-dipole interactions, which caused by fluctuations in adjacent molecules, produced very rapidly
London forces depend on what
- London forces depend on the size/shape of molecules
- (more points of contact between molecules greater forces e.g. unbranched molecules)
- number of electrons however they are always present in a molecules.
As the atomic number increase in isoelectric ions, what happens to the ionic radii
Decreases
Charges increases, meaning nuclear charge increases
N3-, O2-, F-, Na+, Mg2+, Al3+
