Define principal quantum number

A principal quantum number is a number ( n ) that identifies the principal energy level (shell) in which an electron resides. The higher the value of n , the greater the energy of the shell and the further it is from the nucleus .

How many electrons can each of the first four principal quantum shells hold?

The shells hold a maximum of 2 ( n = 1), 8 ( n = 2), 18 ( n = 3) and 32 ( n = 4) electrons respectively. Capacity increases with principal quantum number .

True or False? Each p subshell contains five orbitals, giving a maximum of 10 electrons.

False. The p subshell contains three orbitals, each holding two electrons, giving a maximum of 6 electrons per p subshell.

When electrons are added to a p subshell, they first occupy .......... orbitals singly with .......... spin before pairing up in the same orbital. This is known as .......... .

When electrons are added to a p subshell, they first occupy separate orbitals singly with parallel spin before pairing up in the same orbital. This is known as Hund's Rule .

The ground state is the most stable electron configuration of an atom, achieved when electrons occupy the lowest available energy subshells first.

Why do transition metal atoms lose electrons from the 4s subshell before the 3d subshell when forming ions?

Although the 4s subshell fills before the 3d, once the 3d subshell is occupied it becomes lower in energy than the 4s, so 4s electrons are removed first when transition metals form cations .

Chromium has the electron configuration [Ar] .......... rather than the expected [Ar] 3d 4 4s 2 , because a .......... d subshell is energetically .......... .

Chromium has the electron configuration [Ar] 3d 5 4s 1 rather than the expected [Ar] 3d 4 4s 2 , because a half-full d subshell is energetically favourable .

An ionic bond is the electrostatic attraction between oppositely charged ions, formed by the transfer of electrons from a metal to a non-metal.

What electron configuration do ions formed in ionic bonding typically achieve?

Ions formed in ionic bonding achieve a full outer shell with an electron configuration equivalent to that of the nearest noble gas .

True or False? Ionic bonds are directional, acting only between specific pairs of ions.

False. Ionic bonds are non-directional , meaning the electrostatic attraction between oppositely charged ions acts equally in all directions throughout the lattice.

A giant ionic lattice is a .......... , .......... pattern of alternating cations and anions held together by strong .......... in all directions.

A giant ionic lattice is a regular , repeating pattern of alternating cations and anions held together by strong electrostatic attractions in all directions.

Define giant ionic lattice

A giant ionic lattice is a three-dimensional network of oppositely charged cations and anions held together by strong electrostatic forces of attraction acting in all directions.

Why do ionic compounds with more highly charged ions tend to have higher melting points?

More highly charged ions produce stronger electrostatic attractions between cations and anions, requiring more energy to overcome and resulting in a higher melting point .

True or False? Ionic compounds can conduct electricity when solid.

False. In the solid state, ions are held in fixed positions within the lattice and cannot move, so there are no mobile charge carriers to conduct electricity.

A covalent bond is the electrostatic attraction between the nuclei of bonding atoms and a shared pair of outer-shell electrons.

How does bond length change as bond order increases from single to triple for carbon-carbon bonds?

As bond order increases, bond length decreases because greater electron density pulls the bonded nuclei closer together. Triple bonds are the shortest and strongest carbon-carbon bonds.

True or False? A larger bond energy value indicates a weaker covalent bond.

False. A larger bond energy value indicates a stronger covalent bond, as more energy is required to break one mole of that bond in the gaseous state.

In a dative covalent bond, .......... electrons in the bond come from the .......... atom. The bond is shown using an .......... pointing toward the accepting atom.

In a dative covalent bond, both electrons in the bond come from the same atom. The bond is shown using an arrow pointing toward the accepting atom.

Define dative covalent bond

A dative covalent bond (coordinate bond) is a bond in which both electrons are donated by the same atom , which must possess a lone pair , to an electron-deficient acceptor atom.

How is the ammonium ion, NH 4 + , formed from ammonia and a hydrogen ion?

The nitrogen atom in ammonia donates its lone pair to the electron-deficient H + ion via a dative covalent bond , forming the ammonium ion NH 4 + with a 1+ charge.

True or False? All atoms in covalent molecules obey the octet rule and have exactly 8 electrons in their outer shell.

False. Some atoms can be electron-deficient (e.g. boron in BCl 3 with 6 outer electrons) or have an expanded octet (e.g. sulfur in SO 2 ), so the octet rule has exceptions.

A LevelChemistryOCRFlashcards2. Foundations in ChemistryElectrons, Bonding & Structure

Electrons, Bonding & Structure (OCR A Level Chemistry A): Flashcards

Exam code: H432

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Define principal quantum number

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Define principal quantum number
A principal quantum number is a number (n) that identifies the principal energy level (shell) in which an electron resides. The higher the value of n, the greater the energy of the shell and the further it is from the nucleus.
How many electrons can each of the first four principal quantum shells hold?
The shells hold a maximum of 2 (n = 1), 8 (n = 2), 18 (n = 3) and 32 (n = 4) electrons respectively. Capacity increases with principal quantum number.
True or False?
Each p subshell contains five orbitals, giving a maximum of 10 electrons.
False.
The p subshell contains three orbitals, each holding two electrons, giving a maximum of 6 electrons per p subshell.
When electrons are added to a p subshell, they first occupy .......... orbitals singly with .......... spin before pairing up in the same orbital. This is known as ...........
When electrons are added to a p subshell, they first occupy separate orbitals singly with parallel spin before pairing up in the same orbital. This is known as Hund's Rule.
Define ground state
The ground state is the most stable electron configuration of an atom, achieved when electrons occupy the lowest available energy subshells first.
Why do transition metal atoms lose electrons from the 4s subshell before the 3d subshell when forming ions?
Although the 4s subshell fills before the 3d, once the 3d subshell is occupied it becomes lower in energy than the 4s, so 4s electrons are removed first when transition metals form cations.
Chromium has the electron configuration [Ar] .......... rather than the expected [Ar] 3d⁴4s², because a .......... d subshell is energetically .......... .
Chromium has the electron configuration [Ar] 3d⁵4s¹ rather than the expected [Ar] 3d⁴4s², because a half-full d subshell is energetically favourable.
Define ionic bond
An ionic bond is the electrostatic attraction between oppositely charged ions, formed by the transfer of electrons from a metal to a non-metal.
What electron configuration do ions formed in ionic bonding typically achieve?
Ions formed in ionic bonding achieve a full outer shell with an electron configuration equivalent to that of the nearest noble gas.
True or False?
Ionic bonds are directional, acting only between specific pairs of ions.
False.
Ionic bonds are non-directional, meaning the electrostatic attraction between oppositely charged ions acts equally in all directions throughout the lattice.
A giant ionic lattice is a .......... , .......... pattern of alternating cations and anions held together by strong .......... in all directions.
A giant ionic lattice is a regular, repeating pattern of alternating cations and anions held together by strong electrostatic attractions in all directions.
Define giant ionic lattice
A giant ionic lattice is a three-dimensional network of oppositely charged cations and anions held together by strong electrostatic forces of attraction acting in all directions.
Why do ionic compounds with more highly charged ions tend to have higher melting points?
More highly charged ions produce stronger electrostatic attractions between cations and anions, requiring more energy to overcome and resulting in a higher melting point.
True or False?
Ionic compounds can conduct electricity when solid.
False.
In the solid state, ions are held in fixed positions within the lattice and cannot move, so there are no mobile charge carriers to conduct electricity.
Define covalent bond
A covalent bond is the electrostatic attraction between the nuclei of bonding atoms and a shared pair of outer-shell electrons.
How does bond length change as bond order increases from single to triple for carbon-carbon bonds?
As bond order increases, bond length decreases because greater electron density pulls the bonded nuclei closer together. Triple bonds are the shortest and strongest carbon-carbon bonds.
True or False?
A larger bond energy value indicates a weaker covalent bond.
False.
A larger bond energy value indicates a stronger covalent bond, as more energy is required to break one mole of that bond in the gaseous state.
In a dative covalent bond, .......... electrons in the bond come from the .......... atom. The bond is shown using an .......... pointing toward the accepting atom.
In a dative covalent bond, both electrons in the bond come from the same atom. The bond is shown using an arrow pointing toward the accepting atom.
Define dative covalent bond
A dative covalent bond (coordinate bond) is a bond in which both electrons are donated by the same atom, which must possess a lone pair, to an electron-deficient acceptor atom.
How is the ammonium ion, NH₄⁺, formed from ammonia and a hydrogen ion?
The nitrogen atom in ammonia donates its lone pair to the electron-deficient H⁺ ion via a dative covalent bond, forming the ammonium ion NH₄⁺ with a 1+ charge.
True or False?
All atoms in covalent molecules obey the octet rule and have exactly 8 electrons in their outer shell.
False.
Some atoms can be electron-deficient (e.g. boron in BCl₃ with 6 outer electrons) or have an expanded octet (e.g. sulfur in SO₂), so the octet rule has exceptions.

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