Chemistry - Forces of Attraction

forces of attraction

the interactions that occur between particles and cause them to be drawn to one another — creating a chemical bond

What are the main types of forces of attraction? (4)

ionic bonds, covalent bonds, metallic bonds and van der Waal forces

Describe giant substances in terms of their volatility and solubility (2)

Giant substances are relatively involatile due to the strong forces of attraction between particles

Giant substance can be soluble in polar solvents if their dipoles are partial

Describe molecular substances in terms of their volatility and solubility (2)

Molecular substances are relatively volatile due to the weak forces attraction between molecules

Molecules lack significant dipoles between each other and have are weakly attracted to each other and therefore polar solvents like water cannot interact with them whereas they are soluble in non-polar solvents due to dispersion forces

Describe metals in terms of their volatility and solubility (2)

Metals are relatively involatile due to the strong forces of attraction between the particles in their lattice

These substance are insoluble in both polar and non-polar substances as their atoms can’t interact with a solvent due to their high density

Describe ionic bonding

the instance in which a metal atom transfers its electron to a non-metal atom and ionizes into a positive charged particle while the non-metal ionizes into a negatively charged particle which are held together by electrostatic forces in a three dimensional lattice fueled by the electronegativity of non-metals in which attractive forces interact with charged ions in multiple directions

Describe covalent bonding

the instance in which atoms approach each other and an equilibrium is achieved between the repulsion of their electron clouds and their nuclei resisting each other in the atoms reaching a position of least potential energy where they are sharing electrons in a resultant molecular orbital and a chemical bond persists until sufficient energy is provided to disrupt this dynamic — achieving stability

Describe the relationship between the electronegativity of two atoms and their polarity in a covalent bond

If the electronegativity values of the two atoms in a covalent bond are very similar, they are non-polar. If they are not the same, they are considered polar.

sigma bond

covalent bond formed by the overlap of atomic orbitals alongside a line between the two nuclei

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sigma bond between a s and p orbital

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sigma bond between two p orbitals

pi bond

bond formed from the sideway overlap of p orbitals irrespective of the symmetry about a line joining the two nuclei

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pi bond

Describe the relationship between the type of covalent bond and the amount of bonds between atoms (3/2)

In a single bond, there is one singular sigma bond.
In a double bond, there is one sigma bond and a pi bond.
In a triple bond, there is one sigma bond and two pi bonds.

Sigma bonds will always form first after orbitals overlap end-to-end. After which, pi bonds will form after orbitals interact with each other sideways to form multiple bonds.

coordinate/dative bonding

the instance in which an atom donates a lone pair of electrons to an atom in a covalent bond

metallic bonding

instance in which metals achieve stability via orbitals in metal atoms overlapping to form a band structure where a sea of delocalized electrons can travel throughout the subsequent lattice formed in the metal and hold the metal ions together through electrostatic forces

Describe chemical bonding in terms of orbital overlap

In chemical bonding, two atoms approach each other due to the electrostatic forces of attraction between each other’s nuclei and electrons until an equilibrium is reached after which two molecular orbitals are formed — the bonding orbital and antibonding orbital.

Electrons occupy the bonding orbital as it is closer to the nucleus and has lower energy while electrons do not exist within the antibonding orbital excepts when excited because it is further from the nucleus and serves as a region of repulsion due to its low electron density and role in increasing nucleus-nucleus repulsion.

The net force between the bonding orbital and antibonding orbital keep the molecule stable and the energy difference between the two exists as the band gap.

Describe metallic bonding in terms of orbital overlap

Due to the large atomic radius of metal atoms, they tend to overlap and their low electronegativity allows their electrons to delocalize forming a sea of electrons which oscillate between the two atoms — reducing the energy of the system of two orbitals.

As the energy between the two decreases, the metal atoms approach each other more closely however due to low resistance from the nucleus and rampant electrostatic forces between the delocalized electrons and subsequently formed cations repulsion reduces as electrons evenly distribute between the two orbitals until the bond becomes stable, leading to a complete overlap of the valence and conductive bands

Explain metallic conductivity using energy bands

The overlap of the valence band and conductive band affords electrons enough energy to move across the structure and carry heat and electricity

intermolecular forces

forces of attraction which arise as a result of the attraction between the dipoles of neighbouring molecules

van der Waal forces

umbrella term used to define and categorize the types of attraction between all molecules

Permanent dipole-dipole forces

Keesom forces

weak intermolecular forces that arise between permanently polar molecules when their oppositely charged poles produce electrostatic forces

induced dipole-induced dipole forces

London dispersion forces

interaction in which electrons in a neutral molecule randomly move within it and make it slightly polar whilst its nearby another molecule and a dipole is induced creating a momentary attractive force between them

dipole-induced dipole forces

London dispersion forces

interaction in which a polarized molecule with a charge approaches a neutral molecule or the neutral position of another identical molecule and the charge either repels or attracts nearby electrons leading to a momentary bond

hydrogen bond

instance in which a hydrogen atom covalently bonded to a highly electronegative atom becomes so electron deficient that it gains the ability to interact with a lone pair of electrons on another highly electronegative atom

Describe how hydrogen bonds affect the miscibility, solubility and volatility of water

Substances with hydrogen bonds mix well with other polar substances

Polar molecules capable of hydrogen bonds dissolve easily in water because they can form hydrogen bonds with water molecules

Water has a high melting/boiling point for its size as its hydrogen bonds increase the amount of energy needed to break the bonds between molecules

Describe the role hydrogen bonds play in water’s maximum density

In the case of water, it is at its densest at 4 degrees Celsius due to its arrangement as a liquid in which the increase in thermal energy allows water molecules to exist in continuous motions and only form non-rigid, transient hydrogen bonds with each other and can pack closely together unlike ice molecules which are held in a rigid, open, hexagonal lattice to maximize bonding

VSEPR (2)

valence shell electron pair repulsion theory

model used in chemistry to predict the 3D geometry of simple individual molecules from the number of electron pairs surrounding their central atoms

What are the laws of VSEPR? (3)

Pairs of electrons in the outer shells of the atoms in a molecule repel each other and move as far apart as possible — minimizing repulsive forces in the molecule

Repulsion between lone pairs and lone pairs is greater than repulsion between lone pairs and bond pairs of electrons

Repulsion between lone pairs and bond pairs is greater than repulsion between bond pairs and bond pairs of electrons

Describe the shapes of molecules composed solely of bonding pairs (5)

linear — two bonding pairs with bond angles of 180°

trigonal planar — three bonding pairs with bond angles of 120°

tetrahedral — four bonding pairs arrange themselves in space at maximum distance apart with bond angles of 109.5°

trigonal bipyramidal - five bonding pairs arrange themselves in space at maximum distance apart with three triagonal plane bonds with angles of 120° and two atoms forming linear angles of 180° to each other

octahedral — six bonding pairs arrange themselves with four atoms with bond angles of 90° and two atoms forming linear angles of 180° to each other

Describe the shapes of molecules composed of lone pairs and bonding pairs (4)

trigonal planar — two bonding pairs and a lone pair bond angles less than 120°

tetrahedral — three bonding pairs and a lone pair OR two bond pairs and two lone pairs with bond angles of less than 109.5°

octahedral — four bonding pairs and two lone pairs with square planar bond angles of 90° and linear bond angles of 180°

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linear with two bonding pairs

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trigonal planar with three bonding pairs

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trigonal bipyramidal with five bonding pairs

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tetrahedral with four bonding pairs

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octahedral with six bonding pairs

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trigonal planar with two bond pairs and a lone pair

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tetrahedral with three bond pairs and a lone pair

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octahedral with four bonding pairs and two lone pairs

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tetrahedral with two bonding pairs and two lone pairs

hybridization

a conceptual instance that theorizes that orbitals combine in order to bond more effectively

Describe the hybridization in ethane

In ethane, each C atom forms four sp³ orbitals. Two of these orbitals overlap and the remaining six overlap with the hydrogen atoms in the —CH₃ groups

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orbital diagram of ethane

Describe hybridization in ethene

In ethene, each C atom forms three sp² orbitals that lie 120° apart from each other. These orbitals form two sigma bonds with two hydrogen atoms and one with a carbon atom. A pi bond is formed between the C atoms as well from the overlap of their unhybridized p orbitals

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Orbital diagram of ethene

resonance

instance in which the bonding present in a molecule cannot be expressed in a singular way

Describe hybridization and resonance in benzene (2)

In benzene, the six carbon atoms form a hexagon with three localized sp² orbitals (one to each hydrogen atom and two to other carbon atoms)

The unhybridized p orbitals overlap to form a delocalized system of pi bonds in which electrons can freely move and hence change the amount of bonds present amongst atoms

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Possible structures of benzene

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orbital overlap of benzene