Chem Bonding - created from Mind Map

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Metallic Bond

Defintitin: Metallic Bonding is the electrostatic forces of attraction between the positively charged metal cation and the sea of delocalised electrons

Strong

Physical Properties

Factors

Number of Valence electrons

Charge of Cation

Greater the number of valence electron contributed to the delocalised sea of electrons, the greater the strength of metallic bond

Higher the charge of the metal cation, the stronger the metal electrosatic forces of attraction it has with the delocalised electron, mettallic bond will be stronger

High Mp/Bp

High Electrical Conductivity

Good thermal conductivity

Malleable and Ductile

Metals have giant lattice structure whereby metal atoms pack closely together in a regular structure. A lot of energy is required to break the strong metallic bond resulting in them having high melting and boiling points

Metals are good conductors of electricity due to the presence of delocalised or mobile electrons. These charge carriers are free to move throughout the 3-d structure when a potential difference is applied

Metals are good conductors of heat. Due to the delocalised electrons, when metal is heated at one end, the electrons pick up the thermal energy and vibrate faster. They then collide with the other electrons, passing on the energy to them

Metals can be beaten in to shape when a force is applied. The cations are able too move over one another without breaking metallic bonds

Ionic Bond

Definition: Ionic bonds are electrostatic forces of attraction between an anion and a cation

Ionic solids have giant ionic lattice structure, consisting of regular 3-d arrangement of positive and negative ions forming a giant network. Each ion in the crystal lattice is attracted equally to several surrounding ions of oppositely charge to form a regular 3d giant ionic lattice

Lattice energy

Physical properties

Polarisation

Strength of lattice energy = Product of ionic charge over sum of ionic radius

High Mp/Bp

Solubility

Conductivity

Hard,rigid, Brittle

Ionic compouns are held together by strong electrostatic forces of attraction between oppositely charged ions. Hence, a lot of energy is required to overcome these strong attractions resulting in ionic compound having high mp/bp

Soluble in polar solvent

Not soluble in non polar solvent

When an ionic compound is placed in a polar solvent the solvent can penetrate the crystal lattice and interact with the ions via ion dipole interaction. This ion dipole interaction may release sufficient energy(hydration energy) to overcome the strong ionic bond.

Not all ionic compounds are soluble in water. This happens when the ionic bonds in the lattice is so strong, hydration energy released from forming ion dipole interaction is insufficient to overcome strong ionic bond.

Ionic compounds are not soluble in non-polar solvents as the ion-solvent interactions are too weak, releasing too little energy to overcome the strong electrostatic attractions between the ions int the crystal lattice

Ionic compound conducts electricity in the molten or aqueous state as the ion are free to move. Hence, ionic compounds are good conductors of electricity in the molten or aqueous state

In solid State the ions are held at fixed position and thus unable to act as mobile charge carriers. Hence, ionic compounds do not conduct electricity when in solid state

Ionic compounds are hard due to strong ionic bonds.However a sharp blow will result in a sight displacement along a cleavage plane and bring ions of like charges together. This will then lead to a strong repulsion between planes and cause the ionic crystal lattice to shatter

Occurs when electron cloud of an anion is distorted by a small and highly charged cation which has high polarixing power

Factors

Cation has high charge density greater polarizing power

Anion is large making it more polarizable

Covalent Bond

Simple covalent molecules

electronegativity

Hybridisation

Bond pair

Definition: Electrostatic forces of attraction between shared electron pair and nuclei of both atom

Giant covalent molecule

VSEPR

Factors of Bond strength

Dative Bond

Octet rule exceptions

Id-Id interactions

pd-pd interactions

Hydrogen bond

physical properties

Hydrogen bond>Pd-Pd interactions> id-id interactions

Electrical conductivity

exist in all molecules

weak and short ranged

As electrons are constantly moving, there could be an instataneous dipole formed when there are more electrons on one side of the molecule. Hence there could be a partial charge on atoms, this occurs even for noble gasses. When another neighbouring molecule approaches, the instantaneous dipole can induce a temporary dipole by attracting/repelling its electron

Strength

Molecules which have more electron have larger electron cloud size and can be easily polarised resulting in a stronger id- id interactions

For different molecules with the same number of electrons, id-id interactions are stronger in molecules wtih greater surface area for molecular interactions. Straight chain molecules have a more open structure and hence greater surface area for molecular interactions compared to branched chain isomers which are more compact and spherical.

Polar molecules with non-symmetrical distribution of electrons within the molecule as the atoms have different EN. The more EN atoms will attract electrons towards itself and acquire a partial negative charge, whereas the less EN atom will have a partial positive charge

strength

EN difference between atoms. Greater the difference, the more polar the molecule

magnitude of net dipole moment of molecules

Electrostatic force of attraction between a hydrogen atom covalently bonded to a highly EN atom (F,O,N) and the lone pair electron of another highly EN atom (N,O,F)

Intermolecular hydrogen bond

Intramolecular hydrogen bonds

Factors of strength

Hydrogen bonding in ice

Formation

Formed between the same molecules

Formed between a molecule (that has a hydrogen atom covalently bonded to F,O,N) and a hydrogen bond acceptor.

A hydrogen bond acceptor is a molecule that has no hydrogen atom directly bonded to F,O,N but has a lone pair on F,O,N

Since the 2 substituents are used for intramolecular hydrogen bonding, they have less tendency to attract neighbouring molecules by intermolecular hydrogen bonding

Presence of intramolecular hydrogen bonding, results in less extensive intermolecular hydrogen bonding. The boiling point of the compound would be lower than expected

EN difference between H and (F, O,N), larger the difference stronger the hydrogen bond

number of hydrogen bond per molecule

In ice, hydrogen bonding holds the H2O molecules together in a huge 3-D network. The two lone electron pairs on the same O atom are bonded to the hydrogen atoms of 2 neighbouring molecules by hydrogen bonding. Each water molecule is surrounded by 4 neighbouring molecules in a tetrahedral cluster. The longer H-bonds in the tetrahedral arrangement of the water molecules result in a fairly open structure on ice - a significant amount of empty space leading to a larger volume. When ice melts, the h-bonding in the tetrahedral cluster is partially broken and the molecules become more closely packed ,thus the volume decreases and density increases.

MP/BP

During melting and boiling the weak intermolecular forces of attraction are overcome. The weak Van Der Waals' forces and hydrogen bonding result in a low melting and boiling point

molecular substances are usually non-conductors of electricity due to the absence of mobile particles such as ions or electrons

Gives rise to ionic and covalent character

Polar Bonds

non-polar molecule

When two different atoms of different EN are covalently bonded, the more EN atom pulls the electrons of the covalent bond towards itself and acquires a small negative charge while the other atom acquires a small positive charge

Polarity of a bond is measured by dipole moment

No polar bond in the molecule when all atoms are the same

If two dipoles have the same magnitude and are opposite in direction, they cancel each other. The molecule has a zero overall dipole moment

Hybridization happens when atomic orbitals mix to form new atomic orbitals.

sp3

sp2

sp

Difference in C-C bond length and strength

4 orbitals are connected to the corners of a tetrahedron. each sp3 orbital has a large lobe and a small lobe with a node at the nucleus

Shape: tetrahedral

Three sp2 hybrid orbitals lie in a plane with bond angle 120 degrees

Shape: Trigonal planar

Two sp orbitals lie in straight line with bond angle 180 degrees

Shape: linear

The increasing percentage character of s in the hybrid orbitals results in shorter hybrid orbitals. The greater the percentage of s character, the less diffused the hybrid orbital, the more effective the overlap. Hence leading to stronger the bond energy resulting in a shorter bond length

Sigma bond

Pi Bond

Formed when atomic orbitals overlap in a head-on manner. There can only be one sigma bond between two atoms

Formed when two orbitals overlap in a side-on manner

Weaker than a sigma bond due to less effective side-on over-lap compared to the head-on overlap

pi bond can only be formed after a sigma bond is formed

A giant molecular lattice is held together by a network of covalent bonds

Diamond

Graphite

Each carbon atom is sp3 hybridised and covalently bonded to 4 other carbon atoms forming a tetrahedral. This tetrahedral arrangement is repeated throughout the entire molecule giving rise to interlocking hexagonal units so that the resultant structure is extremely strong and rigid

Electrical conductivity

Melting point

Solubility

does not conduct electricity due to lack of delocalised electrons

3550 degrees celcius due to strong covalent bonds between all the carbon atoms

unable to dissolve as a lot of energy is required to overcome the strong covalent bonds between the carbon atoms

Each carbon atom is sp2 hybridised and forms 3 sigma bonds with 3 other carbon atoms. Hence, the geometry is trigonal planar with bond angles of 120 degrees around each carbon atom. Each carbon atom has an unhybridised p-orbitals of its immediate neighbouring carbon atoms this results in an extended pi electron cloud above and below the plane containing the carbon atoms.

The bonds within each layer are covalent but the attraction between each layer is van der walls forces

melting point

Soft

These pi electrons are delocalised over the entire layer. Graphite is an electrical conductor. However, as the electrons are only delocalised within each layer, graphite can only conduct electricity in a direction parallel to the layers. Graphite is an insulator in a direction pperpendicular to the layers as the delocalised electrons cannot jump across layers

high melting point of 3730 degrees celcius due to presence of strong covalent bonds within each layer which require a lot of energy to overcome

The forces of attraction between each layer, vander waals, are weak. Hence it allows each layer to glide over each other. Thus graphite is soft

Basic principles

no of electron pair

Electron pairs repel each other and arrange themselves as far apart as possible to maximise stability and minimize electronic repulsion

Orbitals containing lone pairs are larger than those containing bond pairs or an odd electron. They take up more space around the central atom and are, on average, closer to the nucleus. Hence they have a greater repulsive effect than the bond pairs

When the bonded atoms are more EN than the central atom, they tend to draw electron density towards themselves. Hence the bond pars are further away from the central atom's nucleus, resulting in a lesser repulsion and smaller bond angle

Lone pair-lone pair repulsion > lone pair- bond pair repulsion > Bod pair bond pair repulsion

1

3

2

4

5

6

180 degree linear

3+0

2+1

120 degree trigonal planar

110-120 degree bent

180 degree linear

4+0

3+1

2+2

109.5 degree tetrahedral

107 degree trigonal pyramidal

105 degree bent

5+0

4+1

3+2

2+3

90, 120 degree trigonal bipyramidal

90, 120 degree see-saw

90 degree T-shaped

180 degree linear

6+0

5+1

4+2

90 degree octahedral

90 degree square pyramidal

90 degree square planar

Effectiveness of overlap

Number of bonding electrons

Bond polarity

shorter bond length

More effective overlap of atomic orbitals

Stronger bond and larger bond energy

Multiple bonds are stronger than single bonds

Greater EN difference between the bonding atoms, stronger the bond

A Dative bond is a covalent bond in which one atom donates a lone pair of electrons for sharing with another atom

Criteria for dative bond sharing

Acts like a covalent bond

Donor atom has a lone pair of electron

The acceptor atom must have an empty shell in the valence shell

Radicals

electron deficient species

Period 3 and after

Chem Bonding