Define electronegativity .

Electronegativity is the ability of an atom to attract a pair of electrons towards itself in a covalent bond.

Which scale is used to measure electronegativity, and what value does it assign to fluorine?

The Pauling scale is used. Fluorine has the highest value of 4.0 , making it the most electronegative element on the periodic table.

True or False? An increased nuclear charge results in a decreased electronegativity.

False. An increased nuclear charge means more protons attract outer electrons more strongly, so electronegativity increases .

Electronegativity .......... across a period and .......... down a group.

Electronegativity increases across a period and decreases down a group.

Define shielding (electronegativity) .

Shielding is the reduction in nuclear attraction experienced by outer electrons due to filled inner energy levels masking the positive charge of the nucleus.

How does atomic radius affect electronegativity?

A larger atomic radius means outer electrons are further from the nucleus and experience weaker attraction, so electronegativity decreases as atomic radius increases.

True or False? Sodium has a higher electronegativity than caesium.

True. Sodium has fewer inner shells than caesium, so its outer electrons experience less shielding and are more strongly attracted to the nucleus.

In the C-F bond of fluoromethane, the bonding electrons are drawn closer to the .......... atom because it has a higher .......... .

In the C-F bond of fluoromethane, the bonding electrons are drawn closer to the fluorine atom because it has a higher electronegativity .

State the three factors that affect the electronegativity of an atom.

Nuclear charge — more protons increase electronegativity. Atomic radius — a larger radius decreases electronegativity. Shielding — more inner shells decrease electronegativity.

Why does electronegativity decrease down a group in the periodic table?

Each successive element has an extra filled electron shell, increasing shielding and atomic radius . Although nuclear charge increases, the overall attraction between the nucleus and outer bonding electrons decreases.

True or False? Shielding increases significantly across a period.

False. Shielding remains reasonably constant across a period because no new electron shells are added.

Across a period, nuclear charge .......... while atomic radius .......... , causing electronegativity to .......... .

Across a period, nuclear charge increases while atomic radius decreases , causing electronegativity to increase .

Define trend in electronegativity across a period .

The trend in electronegativity across a period is the general increase in electronegativity from left to right across a period, driven by increasing nuclear charge with roughly constant shielding.

In which direction on the periodic table is electronegativity at its highest, and which element is the most electronegative?

Electronegativity is greatest towards the top right of the periodic table. Fluorine is the most electronegative element.

True or False? Atomic radius increases across a period.

False. Atomic radius decreases across a period because nuclear charge increases while shielding stays roughly constant, pulling outer electrons closer.

Down a group, shielding .......... and atomic radius .......... , so electronegativity .......... .

Down a group, shielding increases and atomic radius increases , so electronegativity decreases .

What happens to nuclear charge down a group, and why does electronegativity still decrease?

Nuclear charge increases down a group, but the effect is outweighed by the increased shielding and larger atomic radius caused by additional electron shells, reducing the attraction for bonding electrons.

True or False? Nuclear charge increases both across a period and down a group.

True. Nuclear charge increases in both directions as protons are added to the nucleus, but its effect on electronegativity differs because shielding and atomic radius change differently in each direction.

Define polar covalent bond .

A polar covalent bond is a covalent bond in which the bonding electrons are unequally shared due to a difference in electronegativity between the two atoms, creating partial positive (δ + ) and partial negative (δ - ) charges.

What electronegativity difference (ΔEN) range indicates a polar covalent bond?

A ΔEN of approximately 0.4–1.7 indicates a polar covalent bond. Below 0.4 the bond is non-polar covalent; above 1.7 the bond is mostly ionic.

True or False? In H 2 , the bonding electrons are shared equally between the two hydrogen atoms.

True. Both hydrogen atoms have the same electronegativity, so there is no difference in attraction for the bonding electrons, forming a non-polar covalent bond.

In hydrogen fluoride, fluorine carries a partial .......... charge (δ - ) and hydrogen carries a partial .......... charge (δ + ) because fluorine is more .......... .

In hydrogen fluoride, fluorine carries a partial negative charge (δ - ) and hydrogen carries a partial positive charge (δ + ) because fluorine is more electronegative .

Define non-polar covalent bond .

A non-polar covalent bond is a covalent bond formed between two atoms of equal electronegativity, where the bonding electrons are shared equally and no partial charges develop.

How does a large difference in electronegativity between two atoms lead to ionic bond formation?

When ΔEN is large (greater than ~1.7), the more electronegative atom attracts electrons so strongly that the less electronegative atom's electron is transferred completely, forming a cation (positive) and an anion (negative) held by an ionic bond.

True or False? A polar bond always results in a polar molecule.

False. A polar molecule requires that bond dipoles do not cancel out. In some symmetrical molecules, polar bonds cancel, giving a non-polar molecule overall.

A cation is a .......... charged species formed when an atom .......... one or more electrons during ionic bond formation.

A cation is a positively charged species formed when an atom loses one or more electrons during ionic bond formation.

State the type of bond formed when ΔEN ≈ 0 and explain why.

A non-polar covalent bond forms. Both atoms have equal electronegativity so the bonding electrons are shared equally, with no partial charges developing.

A LevelChemistryCambridge (CIE)Flashcards3. Chemical BondingElectronegativity & Bonding

Electronegativity & Bonding (Cambridge (CIE) A Level Chemistry): Flashcards

Exam code: 9701

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Define electronegativity.

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Define electronegativity.
Electronegativity is the ability of an atom to attract a pair of electrons towards itself in a covalent bond.
Which scale is used to measure electronegativity, and what value does it assign to fluorine?
The Pauling scale is used. Fluorine has the highest value of 4.0, making it the most electronegative element on the periodic table.
True or False?
An increased nuclear charge results in a decreased electronegativity.
False.
An increased nuclear charge means more protons attract outer electrons more strongly, so electronegativity increases.
Electronegativity .......... across a period and .......... down a group.
Electronegativity increases across a period and decreases down a group.
Define shielding (electronegativity).
Shielding is the reduction in nuclear attraction experienced by outer electrons due to filled inner energy levels masking the positive charge of the nucleus.
How does atomic radius affect electronegativity?
A larger atomic radius means outer electrons are further from the nucleus and experience weaker attraction, so electronegativity decreases as atomic radius increases.
True or False?
Sodium has a higher electronegativity than caesium.
True.
Sodium has fewer inner shells than caesium, so its outer electrons experience less shielding and are more strongly attracted to the nucleus.
In the C-F bond of fluoromethane, the bonding electrons are drawn closer to the .......... atom because it has a higher .......... .
In the C-F bond of fluoromethane, the bonding electrons are drawn closer to the fluorine atom because it has a higher electronegativity.
State the three factors that affect the electronegativity of an atom.
1. Nuclear charge — more protons increase electronegativity.
2. Atomic radius — a larger radius decreases electronegativity.
3. Shielding — more inner shells decrease electronegativity.
Why does electronegativity decrease down a group in the periodic table?
Each successive element has an extra filled electron shell, increasing shielding and atomic radius. Although nuclear charge increases, the overall attraction between the nucleus and outer bonding electrons decreases.
True or False?
Shielding increases significantly across a period.
False.
Shielding remains reasonably constant across a period because no new electron shells are added.
Across a period, nuclear charge .......... while atomic radius .......... , causing electronegativity to .......... .
Across a period, nuclear charge increases while atomic radius decreases, causing electronegativity to increase.
Define trend in electronegativity across a period.
The trend in electronegativity across a period is the general increase in electronegativity from left to right across a period, driven by increasing nuclear charge with roughly constant shielding.
In which direction on the periodic table is electronegativity at its highest, and which element is the most electronegative?
Electronegativity is greatest towards the top right of the periodic table. Fluorine is the most electronegative element.
True or False?
Atomic radius increases across a period.
False.
Atomic radius decreases across a period because nuclear charge increases while shielding stays roughly constant, pulling outer electrons closer.
Down a group, shielding .......... and atomic radius .......... , so electronegativity .......... .
Down a group, shielding increases and atomic radius increases, so electronegativity decreases.
What happens to nuclear charge down a group, and why does electronegativity still decrease?
Nuclear charge increases down a group, but the effect is outweighed by the increased shielding and larger atomic radius caused by additional electron shells, reducing the attraction for bonding electrons.
True or False?
Nuclear charge increases both across a period and down a group.
True.
Nuclear charge increases in both directions as protons are added to the nucleus, but its effect on electronegativity differs because shielding and atomic radius change differently in each direction.
Define polar covalent bond.
A polar covalent bond is a covalent bond in which the bonding electrons are unequally shared due to a difference in electronegativity between the two atoms, creating partial positive (δ⁺) and partial negative (δ^-) charges.
What electronegativity difference (ΔEN) range indicates a polar covalent bond?
A ΔEN of approximately 0.4–1.7 indicates a polar covalent bond. Below _{0.4 the bond is non-polar covalent; above}1.7 the bond is mostly ionic.
True or False?
In H₂, the bonding electrons are shared equally between the two hydrogen atoms.
True.
Both hydrogen atoms have the same electronegativity, so there is no difference in attraction for the bonding electrons, forming a non-polar covalent bond.
In hydrogen fluoride, fluorine carries a partial .......... charge (δ^-) and hydrogen carries a partial .......... charge (δ⁺) because fluorine is more .......... .
In hydrogen fluoride, fluorine carries a partial negative charge (δ^-) and hydrogen carries a partial positive charge (δ⁺) because fluorine is more electronegative.
Define non-polar covalent bond.
A non-polar covalent bond is a covalent bond formed between two atoms of equal electronegativity, where the bonding electrons are shared equally and no partial charges develop.
How does a large difference in electronegativity between two atoms lead to ionic bond formation?
When ΔEN is large (greater than ~1.7), the more electronegative atom attracts electrons so strongly that the less electronegative atom's electron is transferred completely, forming a cation (positive) and an anion (negative) held by an ionic bond.
True or False?
A polar bond always results in a polar molecule.
False.
A polar molecule requires that bond dipoles do not cancel out. In some symmetrical molecules, polar bonds cancel, giving a non-polar molecule overall.
A cation is a .......... charged species formed when an atom .......... one or more electrons during ionic bond formation.
A cation is a positively charged species formed when an atom loses one or more electrons during ionic bond formation.
State the type of bond formed when ΔEN ≈ 0 and explain why.
A non-polar covalent bond forms. Both atoms have equal electronegativity so the bonding electrons are shared equally, with no partial charges developing.

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