Define covalent bond .

A covalent bond is the electrostatic attraction between the nuclei of two non-metal atoms and their shared pair of electrons in the outer shell.

How many electrons are shared in a single, double and triple covalent bond?

A single bond shares 2 electrons (1 pair), a double bond shares 4 electrons (2 pairs), and a triple bond shares 6 electrons (3 pairs).

True or False? In covalent bonding, electrons are transferred from one atom to the other.

False. In covalent bonding, electrons are shared between the two atoms. Electron transfer occurs in ionic bonding, not covalent bonding.

In N 2 , the two nitrogen atoms share .......... pairs of electrons, forming a .......... covalent bond.

In N 2 , the two nitrogen atoms share three pairs of electrons, forming a triple covalent bond.

What is meant by 'expanding the octet rule', and give one example?

Expanding the octet means a central atom accommodates more than 8 electrons in its outer shell. For example, sulfur in SF 6 has a share of 12 electrons , forming six single S-F bonds.

True or False? Covalent bonding can occur between a metal and a non-metal.

False. Covalent bonding occurs between two non-metals . Bonding between a metal and a non-metal typically involves ionic bonding.

In a dot and cross diagram, .......... represent electrons from one atom and .......... represent electrons from the other atom, and only .......... shell electrons are shown.

In a dot and cross diagram, dots represent electrons from one atom and crosses represent electrons from the other atom, and only outer shell electrons are shown.

Why does PCl 5 have an expanded octet, and how many electrons does phosphorus share in this molecule?

Phosphorus uses available d orbitals to accommodate more than 8 electrons. In PCl 5 , phosphorus forms 5 single bonds and has a share of 10 electrons , exceeding the normal octet.

True or False? Sharing electrons in a covalent bond allows each atom to achieve a noble gas electron configuration.

True. Sharing electrons gives each atom a full outer shell similar to a noble gas configuration, increasing the stability of both atoms.

Define coordinate bond .

A coordinate bond (dative covalent bond) is a covalent bond in which both electrons in the shared pair are donated by the same atom, which must possess a lone pair.

How is the ammonium ion (NH 4 + ) formed, and which atom provides both electrons in the coordinate bond?

The nitrogen atom in ammonia donates its lone pair of electrons to the electron-deficient H + ion, forming a coordinate bond. Both electrons in this bond come from the nitrogen atom, producing NH 4 + .

True or False? In a coordinate bond, the two electrons are contributed one from each atom.

False. In a coordinate bond, both electrons come from the same atom (the donor). This distinguishes it from an ordinary covalent bond.

At lower temperatures, two molecules of AlCl 3 join to form the .......... Al 2 Cl 6 , in which two .......... atoms each donate a lone pair to an aluminium atom.

At lower temperatures, two molecules of AlCl 3 join to form the dimer Al 2 Cl 6 , in which two chlorine atoms each donate a lone pair to an aluminium atom.

Define electron-deficient atom .

An electron-deficient atom is an atom that has an unfilled outer orbital and can therefore accept a lone pair of electrons to form a coordinate bond.

Why does AlCl 3 form a dimer (Al 2 Cl 6 ) at lower temperatures?

AlCl 3 is electron-deficient (aluminium has an incomplete outer shell). At lower temperatures, lone pairs on chlorine atoms of one AlCl 3 molecule form two coordinate bonds with aluminium atoms of a second AlCl 3 molecule, giving the more stable dimer Al 2 Cl 6 .

True or False? Once formed, a coordinate bond is identical in strength and properties to an ordinary covalent bond.

True. After formation, a coordinate bond is indistinguishable from an ordinary covalent bond. The distinction lies only in the origin of the electrons, not in the bond itself.

In a dot and cross diagram, a coordinate bond is shown as an .......... pointing from the .......... pair to the electron-deficient atom.

In a dot and cross diagram, a coordinate bond is shown as an arrow pointing from the lone pair to the electron-deficient atom.

What condition must an atom satisfy to act as an electron pair donor in a coordinate bond?

The atom must possess a lone pair of electrons (a non-bonding pair) in its outer shell that it can donate to an electron-deficient atom.

Define hybridisation .

Hybridisation is the mixing of atomic orbitals within the same shell to form new hybrid orbitals of equal energy, used to explain the bonding and geometry of covalent molecules.

What orbitals combine to form sp 3 hybrid orbitals, and what geometry do they produce?

One s orbital and three p orbitals mix to form four sp 3 hybrid orbitals. These arrange with tetrahedral geometry , giving bond angles of 109.5° (e.g. in methane, CH 4 ).

True or False? A sigma bond is formed by the sideways overlap of p orbitals.

False. A sigma (σ) bond is formed by the end-on (direct) overlap of atomic orbitals. Sideways overlap of p orbitals forms a pi (π) bond .

In ethene, each carbon atom is .......... hybridised, uses .......... hybrid orbitals to form sigma bonds and one unhybridised .......... orbital to form a pi bond.

In ethene, each carbon atom is sp 2 hybridised, uses three hybrid orbitals to form sigma bonds and one unhybridised p orbital to form a pi bond.

Define pi (π) bond .

A pi (π) bond is formed by the sideways overlap of adjacent p orbitals, with electron density distributed above and below the plane of the sigma bond.

How many sigma bonds and pi bonds are in a carbon-carbon triple bond (as in ethyne)?

A triple bond contains one sigma (σ) bond and two pi (π) bonds . The sigma bond arises from end-on overlap and the two pi bonds from sideways overlap of two pairs of p orbitals at right angles to each other.

True or False? sp hybridisation produces a linear geometry with a bond angle of 180°.

True. In sp hybridisation, one s and one p orbital mix to form two sp hybrid orbitals that arrange linearly, giving a bond angle of 180° (e.g. in ethyne).

The .......... the orbital overlap in a covalent bond, the .......... the bond. Sigma bonds have .......... overlap than pi bonds.

The greater the orbital overlap in a covalent bond, the stronger the bond. Sigma bonds have greater overlap than pi bonds.

What hybridisation does nitrogen adopt in ammonia, and how does the lone pair affect the bond angle compared to methane?

Nitrogen in NH 3 is sp 3 hybridised. The lone pair occupies one sp 3 orbital and repels the bonding pairs more strongly than bonding pairs repel each other, reducing the bond angle to 107° (compared to 109.5° in CH 4 ).

Bond energy is the energy required to break one mole of a particular covalent bond in the gaseous state, measured in kJ mol -1 . A larger bond energy indicates a stronger bond.

Bond length is the internuclear distance between two covalently bonded atoms, measured from the nucleus of one atom to the nucleus of the other.

How do bond length and bond energy compare for single, double and triple carbon-carbon bonds?

Going from single to triple bond: bond length decreases (single 147 pm, double 134 pm, triple 120 pm) and bond energy increases (single 347 kJ mol -1 , double 614 kJ mol -1 , triple 839 kJ mol -1 ). Triple bonds are the shortest and strongest.

True or False? A longer bond length corresponds to a stronger covalent bond.

False. A longer bond length means the nuclei are further apart and the attractive forces are weaker, so the bond is weaker . Shorter bonds are stronger.

Triple bonds have a .......... bond length and a .......... bond energy compared to single bonds, because the greater electron density .......... the forces of attraction between nuclei and electrons.

Triple bonds have a shorter bond length and a higher bond energy compared to single bonds, because the greater electron density increases the forces of attraction between nuclei and electrons.

Why does bond energy decrease in the order HCl > HBr > HI?

Going down the halogen group, the atoms become larger. The bonding electrons are further from the nucleus and experience greater shielding, so the attractive force between bonding electrons and nucleus decreases , making the bond easier to break.

True or False? HI is more reactive than HCl because it has a shorter bond length.

False. HI has a longer bond length (0.161 nm vs 0.127 nm for HCl) and a lower bond energy, meaning less energy is needed to break the bond, making HI more reactive .

The reactivity of a covalent bond is influenced by its .......... , its .......... and the bond .......... (sigma or pi).

The reactivity of a covalent bond is influenced by its polarity , its strength and the bond type (sigma or pi).

What units are used for bond energy, and what does a higher value tell you about the bond?

Bond energy is measured in kJ mol -1 . A higher value means the bond requires more energy to break, indicating a stronger covalent bond.

A LevelChemistryCambridge (CIE)Flashcards3. Chemical BondingCovalent Bonding & Coordinate (Dative Covalent) Bonding

Covalent Bonding & Coordinate (Dative Covalent) Bonding (Cambridge (CIE) A Level Chemistry): Flashcards

Exam code: 9701

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Define covalent bond.

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Cards in this collection (36)

Define covalent bond.
A covalent bond is the electrostatic attraction between the nuclei of two non-metal atoms and their shared pair of electrons in the outer shell.
How many electrons are shared in a single, double and triple covalent bond?
A single bond shares 2 electrons (1 pair), a double bond shares 4 electrons (2 pairs), and a triple bond shares 6 electrons (3 pairs).
True or False?
In covalent bonding, electrons are transferred from one atom to the other.
False.
In covalent bonding, electrons are shared between the two atoms. Electron transfer occurs in ionic bonding, not covalent bonding.
In N₂, the two nitrogen atoms share .......... pairs of electrons, forming a .......... covalent bond.
In N₂, the two nitrogen atoms share three pairs of electrons, forming a triple covalent bond.
What is meant by 'expanding the octet rule', and give one example?
Expanding the octet means a central atom accommodates more than 8 electrons in its outer shell. For example, sulfur in SF₆ has a share of 12 electrons, forming six single S-F bonds.
True or False?
Covalent bonding can occur between a metal and a non-metal.
False.
Covalent bonding occurs between two non-metals. Bonding between a metal and a non-metal typically involves ionic bonding.
In a dot and cross diagram, .......... represent electrons from one atom and .......... represent electrons from the other atom, and only .......... shell electrons are shown.
In a dot and cross diagram, dots represent electrons from one atom and crosses represent electrons from the other atom, and only outer shell electrons are shown.
Why does PCl₅ have an expanded octet, and how many electrons does phosphorus share in this molecule?
Phosphorus uses available d orbitals to accommodate more than 8 electrons. In PCl₅, phosphorus forms 5 single bonds and has a share of 10 electrons, exceeding the normal octet.
True or False?
Sharing electrons in a covalent bond allows each atom to achieve a noble gas electron configuration.
True.
Sharing electrons gives each atom a full outer shell similar to a noble gas configuration, increasing the stability of both atoms.
Define coordinate bond.
A coordinate bond (dative covalent bond) is a covalent bond in which both electrons in the shared pair are donated by the same atom, which must possess a lone pair.
How is the ammonium ion (NH₄⁺) formed, and which atom provides both electrons in the coordinate bond?
The nitrogen atom in ammonia donates its lone pair of electrons to the electron-deficient H⁺ ion, forming a coordinate bond. Both electrons in this bond come from the nitrogen atom, producing NH₄⁺.
True or False?
In a coordinate bond, the two electrons are contributed one from each atom.
False.
In a coordinate bond, both electrons come from the same atom (the donor). This distinguishes it from an ordinary covalent bond.
At lower temperatures, two molecules of AlCl₃ join to form the .......... Al₂Cl₆, in which two .......... atoms each donate a lone pair to an aluminium atom.
At lower temperatures, two molecules of AlCl₃ join to form the dimer Al₂Cl₆, in which two chlorine atoms each donate a lone pair to an aluminium atom.
Define electron-deficient atom.
An electron-deficient atom is an atom that has an unfilled outer orbital and can therefore accept a lone pair of electrons to form a coordinate bond.
Why does AlCl₃ form a dimer (Al₂Cl₆) at lower temperatures?
AlCl₃ is electron-deficient (aluminium has an incomplete outer shell). At lower temperatures, lone pairs on chlorine atoms of one AlCl₃ molecule form two coordinate bonds with aluminium atoms of a second AlCl₃ molecule, giving the more stable dimer Al₂Cl₆.
True or False?
Once formed, a coordinate bond is identical in strength and properties to an ordinary covalent bond.
True.
After formation, a coordinate bond is indistinguishable from an ordinary covalent bond. The distinction lies only in the origin of the electrons, not in the bond itself.
In a dot and cross diagram, a coordinate bond is shown as an .......... pointing from the .......... pair to the electron-deficient atom.
In a dot and cross diagram, a coordinate bond is shown as an arrow pointing from the lone pair to the electron-deficient atom.
What condition must an atom satisfy to act as an electron pair donor in a coordinate bond?
The atom must possess a lone pair of electrons (a non-bonding pair) in its outer shell that it can donate to an electron-deficient atom.
Define hybridisation.
Hybridisation is the mixing of atomic orbitals within the same shell to form new hybrid orbitals of equal energy, used to explain the bonding and geometry of covalent molecules.
What orbitals combine to form sp³ hybrid orbitals, and what geometry do they produce?
One s orbital and three p orbitals mix to form four sp³ hybrid orbitals. These arrange with tetrahedral geometry, giving bond angles of 109.5° (e.g. in methane, CH₄).
True or False?
A sigma bond is formed by the sideways overlap of p orbitals.
False.
A sigma (σ) bond is formed by the end-on (direct) overlap of atomic orbitals. Sideways overlap of p orbitals forms a pi (π) bond.
In ethene, each carbon atom is .......... hybridised, uses .......... hybrid orbitals to form sigma bonds and one unhybridised .......... orbital to form a pi bond.
In ethene, each carbon atom is sp² hybridised, uses three hybrid orbitals to form sigma bonds and one unhybridised p orbital to form a pi bond.
Define pi (π) bond.
A pi (π) bond is formed by the sideways overlap of adjacent p orbitals, with electron density distributed above and below the plane of the sigma bond.
How many sigma bonds and pi bonds are in a carbon-carbon triple bond (as in ethyne)?
A triple bond contains one sigma (σ) bond and two pi (π) bonds. The sigma bond arises from end-on overlap and the two pi bonds from sideways overlap of two pairs of p orbitals at right angles to each other.
True or False?
sp hybridisation produces a linear geometry with a bond angle of 180°.
True.
In sp hybridisation, one s and one p orbital mix to form two sp hybrid orbitals that arrange linearly, giving a bond angle of 180° (e.g. in ethyne).
The .......... the orbital overlap in a covalent bond, the .......... the bond. Sigma bonds have .......... overlap than pi bonds.
The greater the orbital overlap in a covalent bond, the stronger the bond. Sigma bonds have greater overlap than pi bonds.
What hybridisation does nitrogen adopt in ammonia, and how does the lone pair affect the bond angle compared to methane?
Nitrogen in NH₃ is sp³ hybridised. The lone pair occupies one sp³ orbital and repels the bonding pairs more strongly than bonding pairs repel each other, reducing the bond angle to 107° (compared to 109.5° in CH₄).
Define bond energy.
Bond energy is the energy required to break one mole of a particular covalent bond in the gaseous state, measured in kJ mol^-1. A larger bond energy indicates a stronger bond.
Define bond length.
Bond length is the internuclear distance between two covalently bonded atoms, measured from the nucleus of one atom to the nucleus of the other.
How do bond length and bond energy compare for single, double and triple carbon-carbon bonds?
Going from single to triple bond: bond length decreases (single _{147 pm, double}134 pm, triple _{120 pm) and bond energy}_increases_(single347 kJ mol^-1, double _{614 kJ mol}^_-1_{, triple}839 kJ mol^-1). Triple bonds are the shortest and strongest.
True or False?
A longer bond length corresponds to a stronger covalent bond.
False.
A longer bond length means the nuclei are further apart and the attractive forces are weaker, so the bond is weaker. Shorter bonds are stronger.
Triple bonds have a .......... bond length and a .......... bond energy compared to single bonds, because the greater electron density .......... the forces of attraction between nuclei and electrons.
Triple bonds have a shorter bond length and a higher bond energy compared to single bonds, because the greater electron density increases the forces of attraction between nuclei and electrons.
Why does bond energy decrease in the order HCl > HBr > HI?
Going down the halogen group, the atoms become larger. The bonding electrons are further from the nucleus and experience greater shielding, so the attractive force between bonding electrons and nucleus decreases, making the bond easier to break.
True or False?
HI is more reactive than HCl because it has a shorter bond length.
False.
HI has a longer bond length (0.161 nm vs 0.127 nm for HCl) and a lower bond energy, meaning less energy is needed to break the bond, making HI more reactive.
The reactivity of a covalent bond is influenced by its .......... , its .......... and the bond .......... (sigma or pi).
The reactivity of a covalent bond is influenced by its polarity, its strength and the bond type (sigma or pi).
What units are used for bond energy, and what does a higher value tell you about the bond?
Bond energy is measured in kJ mol^-1. A higher value means the bond requires more energy to break, indicating a stronger covalent bond.

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