Structure and bonding Flashcards
What is an ionic bond
electrostatic forces of attraction between oppositely-charged ions.
Why are ionic bonnds formed
elements having a large difference in electronegativity.
How are ionic compounds arranged
in a three-dimensional crystalline structure, known as an ionic lattice
What is the term coordination number used to signify
the number of ions that surround a given ion in an ionic lattice.
What is Charge density
the charge per unit volume of an ionic compound
Do ionic compounds have high or low melting and boiling points and why
Very high because electrostatic forces of attraction between the ions is very strong and requires high amounts of energy to break.
The two factors that determine the melting point of an ionic compound are what
the ionic radius and the charge on the ion.
Ionic radius and melting point are inverse or direct
inverse
Charge on the ion are inverse or direct
direct
Ionic compounds are soluble in what kinds of substances and why
polar solvents because the ions are attracted to the charged molecules and so the ions dissociate in solvent, and the lattice breaks down.
What are ionic compounds not soluble in
Non-polar substances
Can ionic compounds conduct electricity when solid and why.
They cannot conduct electricity in solid state because the ions are firmly held in the lattice and are unable to move, and therefore cannot carry charges.
Can ionic compounds conduct electricity when aqueous or liquid and why.
they are able to conduct electricity due to prescence of free ions that are able to move and carry charges
Are ionic substances brittle and why
Yes because when force is applied, ions of the same charge get moved next to each other in the structure and so the repulsive forces exerted by the ions causes the lattice to split.
What does brittle mean
the substance tends to shatter when force is applied.
The ionic character of any element is determined by what
the difference in electronegativity between the atoms in the compound.
Is ionic character and the difference in electronegativity inverse or direct
direct
An ionic compound containing polyatomic ions has 2 types of bonding. What are they?
ionic and covalent
The atoms in the polyatomic ions are bonded how
covalently
the polyatomic ion itself and the other ion are bonded how.
ionically
What is a covalent bond
electrostatic forces of attraction between the positively charged nucleus and the shared pair of electrons.
Covalent bonding usually occurs between what
non-metals
name the three types of covalent bonds
single, double, and triple
are Bond length and bond strength inverse or direct and why
inverse because Longer bonds are weaker than shorter bonds because as bond length increases, the distance of the shared pair of electrons from the nucleus increases, which reduces the bond strength.
In a lewis dot structure Central atom must be what
of large size, or least electronegative, or least in number.
List examples of elements that can be central atoms in a lewis dot structure (8)
Oxygen, sulphur, phosphorous, nitrogen, silicon, carbon, chlorine, iodine
In a lewis dot structure what must be filled first
The octet of the corner
in a lewis dot structure how many atoms can the central atom have and how many can the corner atoms have
central atom can have 8 or more electrons (if expanded octet), but corner atoms can only have 8.
Why does a central atom try to remain in maximum co-valency
To form the maximum number of covalent bonds it can.
which atoms do the positive and negative charges go on
if there is a positive charge it is always on the central atom while every negative charge is on the corner atoms.
what is a Coordinate covalent bond
a bond where both the shared electrons are provided by the one of the atom
electron-deficient meaning
it has less electrons in its valence shell and has an incomplete octet
When do coordinate covalent bonds occur, and which elements do not satisfy the octet rule (4)
when one atom in a molecule is electron-deficient. The elements that do not satisfy the octet rule are H (Hydrogen), He (Helium), B (Boron), and Be (Beryllium)
what is the bond order
it is the number of bonds between 2 atoms.
Single bonds have a bond order of ?, double bonds have a bond order of ?, and triple bonds have a bond order of ?.
1, 2, 3
Bond order for a molecule can be calculated by what sum
Bond order=sum of individual bond orders/number of bonding groups
what is the Octet rule
the most stable arrangement for an atom to have in its outermost shell is 8 electrons.
Which atoms can have expanded octets, and how many valence electrons can such molecules have
Atoms from Period 3 and beyond can have expanded octets. Such molecules can have up to 18 valence electrons.
Electron domains consist of what
single, double, or triple bonds and lone pairs.
How are electron domains counted in terms of bonds
Each single bond, double bond, and triple bond is considered one electron domain, regardless of the number of shared electron pairs
There is what between electron domains.
repulsion
The total amount of electron domains around the central atom of the molecule determines the what
the electron domain geometry
The molecule’s shape is determined by what
the bond angle between the atoms bonded to the central atom
Why do lone pairs have greater repulsion forces compared to bonding pairs
Lone pairs have a higher concentration of charge because they are not shared between atoms. This makes their repulsive forces greater than those of bonding pairs
Why do bond pairs have lesser repulsion forces compared to lone pairs?
Bond pairs (such as single, double, or triple bonds) involve shared electrons, so the concentration of charge is considerably lesser, resulting in weaker repulsive forces compared to lone pairs.
In descending order of repulsion, the electron domains are
Lone pair-lone pair > Lone pair-bond pair > Bond pair-bond pair
How do lone pairs affect bond angles in a molecule?
Lone pairs repel bond pairs more strongly than bond pairs repel each other, which reduces the bond angle between the bonded atoms around the central atom.
The molecule will always take the shape which will minimise repulsion between what
electron domains
In two electron domains, what is the electron domain geometry, molecular geometry, and bond angle
linear, linear, 180
For molecules with 3 electron domains, the electron domain geometry is always what
trigonal planar
What is the electron domain geometry and the molecular geometry when there are 3 bond pairs
trigonal planar, trigonal planar
What is the bond angle when there are 3 bond pairs
120
What is the electron domain geometry and the molecular geometry when there are 2 bond pairs and 1 lone pair
trigonal planar, bent (v-shaped)
What is the bond angle when there are 2 bond pairs and 1 lone pair
118
For molecules with 4 electron domains, the electron domain geometry is always what.
tetrahedral
What is the electron domain geometry and the molecular geometry when there are 4 bond pairs
tetrahedral, tetrahedral
What is the bond angle when there are 4 bond pairs
109.5
What is the electron domain geometry and the molecular geometry when there are 3 bond pairs and 1 lone pair
tetrahedral, trigonal pyramidal
What is the bond angle when there are 3 bond pairs and 1 lone pair
107
What is the electron domain geometry and the molecular geometry when there are 2 bond pairs and 2 lone pairs
tetrahedral, bent (v-shaped)
What is the bond angle when there are 2 bond pairs and 2 lone pairs
104.5
Polarity depends on the difference in what between two atoms.
electronegativity
What is considered a high electronegativity difference and what does that mean about the bond
(>1.8), the bond is ionic.
What is considered a low electronegativity difference and what does that mean about the bond
(<0.5) the bond is pure covalent (0) or weakly polar covalent (between 0 and 0.5)
if the electronegativity is between 0.5 and 1.8 what does it mean about the bond
the bond is polar covalent
Why does polarity occur in a bond
the difference in electronegativity between the atoms causes unequal sharing of electrons. The electron cloud is attracted towards the more electronegative atom, creating a bond dipole.
What do bond dipoles result in, and how are partial charges assigned
Bond dipoles result in atoms having partial positive (δ⁺) or partial negative (δ⁻) charges. The more electronegative atom gains a partial negative charge, while the less electronegative one gains a partial positive charge.
The polarity of a molecule depends on what two things
the electronegativity difference between the atoms.
the orientation of the polar bonds within the molecule.
If the molecule contains no polar bonds, it is what
strictly non-polar
When is a molecule considered non-polar despite having polar bonds
A molecule is considered non-polar if it contains polar bonds but is arranged in a perfectly symmetrical way, causing the polar moments of each bond to cancel out.
When is a molecule considered polar when it has polar bonds
A molecule is considered polar if it contains polar bonds but has an asymmetrical orientation.
when does resonance occur
when more than one valid Lewis structure can be drawn for a particular molecule.
what does resonance mean
that a certain bond(such as a double bond) has equal probability of being in different places, and so each bond is in between a single and a double bond.
Why are molecules with resonance structures more stable?
In resonance hybrid structures, the electrons are not confined to one location and can occupy different positions. This delocalization of electrons makes the molecule more stable.
What is the bonding structure of carbon atoms in diamond (including molecular geometry and bond angles)
Each carbon atom in diamond is bonded to 4 other carbon atoms in a tetrahedral structure with bond angles of 109.5°.
What type of structure does diamond have
giant covalent
What are the melting and boiling points of diamond
Diamond has a high melting point and high boiling point
Why is diamond a non-conductor of electricity
Diamond is a non-conductor of electricity because all the electrons are bonded and cannot move.
What is diamond’s thermal conductivity like
Diamond is a great thermal conductor.
What are the physical properties of diamond
Diamond is extremely hard and brittle.
What is diamond’s appearance
Diamond is a transparent crystal.
What are some uses of diamond
Diamond is used for glass cutting and for ornaments.
How are the carbon atoms bonded in graphite
Each carbon atom in graphite is bonded to 3 other carbon atoms
What is the bonding arrangement and bond angles in graphite
Graphite forms hexagonal structures with bond angles of 120°.
How is graphite structured in terms of layers
Graphite has many layers.
What type of structure does graphite have
Graphite has a giant covalent structure
What are the melting and boiling points of graphite
Graphite has a high melting point and high boiling point.
Why is graphite a good conductor of electricity
Graphite is a good conductor of electricity due to the presence of mobile electrons.
Is graphite a good conductor of heat
No, graphite is not a good conductor of heat.
What is the physical property of graphite that makes it soft and slippery
Graphite is soft and slippery due to its many layers that can slip over each other
What is the appearance of graphite
Graphite is a dark grey shiny solid.
What are some uses of graphite
Graphite is used as a lubricant and in pencils.
How are the carbon atoms bonded in graphene
Each carbon atom in graphene is bonded to 3 other carbon atoms.
What is the bonding arrangement and bond angles in graphene
Graphene forms hexagonal structures with bond angles of 120°.
How many layers does graphene have
Graphene has only one layer, making it a two-dimensional structure.
What is the electrical conductivity of graphene
Graphene is a good electrical conductor
What is the thermal conductivity of graphene
Graphene is the best thermal conductor.
What are the melting and boiling points of graphene
Graphene has a high melting point and high boiling point.
What is the transparency of graphene like
Graphene is almost fully transparent.
What are the physical properties of graphene
Graphene is flexible and has high tensile strength.
What are some uses of graphene
Graphene is used in photovoltaic cells and many electronic devices.
How are the carbon atoms bonded in Fullerene (C₆₀)
In Fullerene (C₆₀), each carbon atom is bonded in a sphere of 60 carbon atoms, consisting of 12 pentagons and 20 hexagons.
What is the electrical conductivity of Fullerene
Fullerene is a semi-conductor due to some electron mobility.
What is the thermal conductivity of Fullerene
Fullerene has very low thermal conductivity.
What are the melting and boiling points of Fullerene
Fullerene has low melting and low boiling points.
What are the physical properties of Fullerene
Fullerene is flexible and appears as a yellow, crystalline solid.
What are some uses of Fullerene
Fullerene is used in lubricants and nano-technology.
Which substances are examples of giant covalent structures (4)
diamond, graphite, silicon, and silicon dioxide (SiO₂).
What are the general properties of giant covalent structures (4)
High melting and boiling points
Very hard
Insoluble in water
Non-conductors of electricity
How are the silicon atoms bonded in silicon (including molecular geometry and bond angle)
Each silicon atom is bonded to 4 other silicon atoms covalently in a tetrahedral structure with a bond angle of 109.5°.
What is the electrical conductivity of silicon
Silicon is a poor conductor of electricity due to low electron mobility.
What are the physical properties of silicon
Silicon is extremely hard and brittle.
What are the melting and boiling points of silicon
Silicon has high melting and boiling points.
How are the atoms bonded in Silicon Dioxide (SiO₂) (including molecular geometry and bond angles)
In Silicon Dioxide (SiO₂), each silicon atom is bonded to 4 oxygen atoms, and each oxygen atom is bonded to 2 silicon atoms in a tetrahedral structure with a bond angle of 109.5°.
What are the physical properties of Silicon Dioxide (SiO₂)
Silicon Dioxide (SiO₂) is very hard and brittle.
What are the melting and boiling points of Silicon Dioxide (SiO₂)
Silicon Dioxide (SiO₂) has high melting and boiling points.
What is the electrical conductivity of Silicon Dioxide (SiO₂)
Silicon Dioxide (SiO₂) is a non-conductor of electricity.
Physical properties of covalent compounds are mainly because of their what
intermolecular forces
Why do covalent compounds have relatively low melting and boiling points?
Covalent compounds have relatively low melting and boiling points due to weak intermolecular forces.
How do non-polar substances dissolve in non-polar solvents
Non-polar substances dissolve in non-polar solvents through the formation of London Dispersion forces between them.
How do polar substances dissolve in polar solvents
Polar substances generally dissolve in polar solvents due to dipole interactions and hydrogen bonding.
Why are covalent compounds unable to conduct electricity
Covalent compounds cannot conduct electricity because they do not have any free ions in any state.
What is an exception to the rule that covalent compounds cannot conduct electricity?
An exception is HCl (hydrochloric acid), which can conduct electricity due to the ionization in aqueous solution.
Intermolecular forces refer to what
the forces that hold the molecules together
How do intermolecular forces affect the physical properties of substances?
Intermolecular forces affect physical properties such as volatility, solubility, and conductivity.
Where do London Dispersion Forces exist
London Dispersion Forces exist between all atoms and molecules.
What causes London Dispersion Forces
London Dispersion Forces are caused by instantaneous or temporary dipoles, where the electron density in a molecule changes momentarily, leading to temporary partial charges (δ⁺ and δ⁻).
How do London Dispersion Forces form in non-polar molecules like Cl₂
In Cl₂, there are no permanent dipoles, but the electron density can change temporarily, inducing temporary dipoles in neighboring molecules, which then experience forces of attraction.
What factors influence the strength of London Dispersion Forces
And how do these factors affect them
Polarisability (ease with which temporary dipoles can form). The greater the molar mass of the molecule, the greater the polarisability.
Surface area of the molecule. Molecules with greater surface area have stronger London Dispersion Forces.
How does polarisability affect London Dispersion Forces
Larger polarisability leads to the formation of larger induced dipoles, which results in stronger London Dispersion Forces.
Where do dipole-dipole forces exist
Dipole-dipole forces only exist in polar molecules, as they have permanent dipoles.
How do dipole-dipole forces work
Dipole-dipole forces occur when molecules are attracted to each other due to the opposite charges of their permanent dipoles.
How do the strength of dipole-dipole forces compare to London Dispersion forces
Dipole-dipole forces are stronger than London Dispersion forces.
Where does hydrogen bonding occur
(give 3 examples)
Hydrogen bonding occurs between polar molecules that contain an atom with a lone pair, such as O, N, or F.
How does hydrogen bonding work
In hydrogen bonding, the lone pair of electrons on an atom (like O, N, or F) has a negative charge, while another molecule’s atom has a permanent positive charge (δ⁺). They attract, forming a hydrogen bond.
How does the strength of hydrogen bonds compare to other intermolecular forces
Hydrogen bonds are the strongest of the three, followed by dipole-dipole forces, and then London (dispersion) forces.
Hydrogen bonds > Dipole-dipole forces > London (dispersion) forces
What effect do hydrogen bonds have on the melting and boiling points of substances
Hydrogen bonding leads to high melting and boiling points.
What is metallic bonding
Metallic bonding involves electrostatic forces of attraction between a lattice of cations and a sea of delocalized electrons.
What two factors determine the strength of a metallic bond and how do they affect the bond
Charge on the metal ion: The greater the charge on the metal ion, the stronger the electrostatic attraction and the stronger the metallic bond.
Ionic radius: If the ionic radius of the metal ion increases, the distance between the cation and the delocalized electrons increases, weakening the attraction and decreasing the strength of the metallic bond.
Why are metals good conductors of electricity
Metals are good conductors of electricity due to the presence of delocalized electrons which are highly mobile.
Why are metals good thermal conductors
Metals are good thermal conductors because delocalized electrons and cations are close together, enabling efficient transfer of energy.
Why are metals malleable and ductile
Metals are malleable and ductile because the delocalized electrons move randomly and non-directionally, so the metallic bond does not break when the shape changes.
Why do metals have high melting and boiling points
Metals have high melting and boiling points because the electrostatic forces of attraction between cations and delocalized electrons are very strong, requiring a lot of energy to break the metallic bonds.
Why are metals shiny and lustrous
Metals are shiny and lustrous because the delocalized electrons reflect light.
How are alloys made
Alloys are made by adding a metal element to another element in a molten state. When the homogeneous mixture solidifies, the metal becomes very hard, and the layers cannot slide over each other easily.
What is Brass and what are its properties
Brass is an alloy of 70% copper and 30% zinc. It is harder than pure copper.
What is Bronze and what are its properties
Bronze is an alloy of 90% copper and 10% tin. It is harder than pure copper.
What is Mild Steel and what are its properties
Mild Steel is an alloy of 99.7% iron and 0.3% carbon. It is stronger and harder than pure iron.
What is Stainless Steel and what are its properties
Stainless Steel is an alloy of 74% iron, 18% chromium, and 8% nickel. It has increased resistance to corrosion and is commonly used to make cutlery.
What types of elements can expand their octets, and how many electron domains can they have?
Elements like sulfur and phosphorus can expand their octets and have 5-6 electron domains.
What is the electron domain geometry and bond angles for a molecule with 5 electron domains
The electron domain geometry is triangular bipyramidal, with bond angles of 90°, 120°..
What is the molecular geometry and bond angles of a molecule with 4 bonding pairs and 1 lone pair
The molecular geometry is see-saw, with bond angles of 119°, 89°
Example: SF₄
What is the molecular geometry and bond angles of a molecule with 3 bonding pairs and 2 lone pairs?
The molecular geometry is T-shaped, with bond angles of 89° and 120°.
Example: ClF₃
What is the molecular geometry and bond angles of a molecule with 2 bonding pairs and 3 lone pairs?
The molecular geometry is linear, with a bond angle of 180°.
Example: I₃⁻
What is the electron domain geometry and bond angles for a molecule with 6 electron domains?
The electron domain geometry is octahedral, with bond angles of 90°.
What is the molecular geometry of a molecule with 5 bonding pairs and 1 lone pair?
The molecular geometry is square pyramidal
What is the molecular geometry of a molecule with 4 bonding pairs and 2 lone pairs?
The molecular geometry is square planar.
How can molecular polarity be determined
If no lone pairs are present, the molecule is usually non-polar.
If lone pairs are present, the molecule is often polar, unless symmetry cancels out the dipoles
What is the formula for calculating Formal Charge?
FC = V - (1/2B + L)
V = Valence electrons
B = Bonding electrons
L = Lone pair electrons
What does a low formal charge indicate about a molecule
A low formal charge means less charge transfer occurred during the formation of the molecule, making the structure more stable and preferred.
What is a Sigma Bond and how and where is it formed?
Where is the elctron density concentrated?
What types of bonds are they present in?
A Sigma bond is formed when two atomic orbitals overlap head-on along the bond axis.
The electron density is concentrated between the nuclei of the bonded atoms.
Sigma bonds are present in single, double, and triple bonds.
Where is the electron density in a Sigma bond?
The electron density in a Sigma bond is concentrated between the nuclei of the bonded atoms.
What is a Pi bond and how is it formed?
A Pi bond is formed when two p orbitals overlap sideways above and/or below the bond axis.
Where is the electron density in a pi bond?
The electron density is concentrated in two regions—above and/or below the plane of the bond axis.
When does a Pi bond form?
A Pi bond forms only alongside the formation of a Sigma bond, meaning it can only form in a double or triple bond.
How many Sigma and Pi bonds are there in a double bond?
A double bond contains one Sigma bond and one Pi bond.
How many Sigma and Pi bonds are there in a triple bond?
A triple bond contains one Sigma bond and two Pi bonds.
What is Hybridization?
Hybridization is the process by which atomic orbitals within an atom mix to produce hybrid orbitals of intermediate energy.
How does Hybridization affect covalent bonds?
Covalent bonds formed with hybridized orbitals are often stronger than those formed with unhybridized orbitals.
What is Excitation in terms of covalent bond formation?
Excitation is the process where electrons are promoted to higher energy levels to maximize bonding. For example, in carbon, an electron from the 2s orbital moves to the 2p orbital, making four unpaired electrons available for bonding.
Why is Excitation important for bond formation?
Excitation allows atoms to have unpaired electrons, which are required for bonding. The energy needed for excitation is compensated by the energy released during bond formation.
What happens after Excitation in terms of orbital overlap?
After excitation, the atomic orbitals available for bonding are not identical. To resolve this, the orbitals mix to form new hybrid orbitals that are identical to each other, but different from the original orbitals.
How does Hybridization resolve the issue of unequal bond formation?
By mixing orbitals of different types and energy levels, Hybridization creates identical hybrid orbitals that form stronger and more equal bonds than the original unhybridized orbitals.
What kind of bond does the overlap of a hybrid orbital form?
The overlap of a hybrid orbital with any other orbital always forms a Sigma bond.
What is SP³ Hybridization?
SP³ Hybridization is the mixing of one s-orbital and three p-orbitals.
Example: Carbon (C) in CH₄ (methane).
What is the geometry of a molecule with SP³ Hybridization?
The orbitals in SP³ Hybridization orient themselves at 109.5°, forming a tetrahedral geometry.
What is SP² Hybridization?
What types of bonds do you see this in?
SP² Hybridization is the mixing of one s-orbital and two p-orbitals. This type of hybridization is often seen in molecules with double bonds.
Example: Carbon (C) in C₂H₄ (ethylene)
What is the molecular geometry and bond angle of a molecule with SP² Hybridization?
In SP² Hybridization, the orbitals orient themselves at 120°, forming a trigonal planar geometry.
How do unhybridized orbitals behave in SP² Hybridization?
In SP² Hybridization, the one p-orbital that did not hybridize remains unhybridized and can form a pi bond.
What is SP Hybridization?
What type of bond is this common in?
SP Hybridization is the mixing of one s-orbital and one p-orbital. This type of hybridization is commonly seen in molecules with triple bonds.
Example: Carbon (C) in C₂H₂ (acetylene).
What is the molecular geometry and bond angle of a molecule with SP Hybridization?
In SP Hybridization, the orbitals orient themselves at 180°, forming a linear geometry.
How do unhybridized orbitals behave in SP Hybridization?
In SP Hybridization, the two p-orbitals that did not hybridize remain unhybridized and can form pi bonds.
