Electronegativity and bonding
Introduced| English | Meaning |
|---|---|
| electronegativity/ɪˌlektrəʊŋɡəˈtɪvɪti/ | The tendency of an atom in a chemical bond to attract the shared electrons towards itself. |
| nuclear charge/ˈnjuːklɪə tʃɑːdʒ/ | The total positive charge of an atomic nucleus, determined by its number of protons. |
| ionic bond/aɪˈɒnɪk bɒnd/ | The electrostatic attraction between oppositely charged ions. |
| covalent bond/ˈkəʊvələnt bɒnd/ | A chemical bond involving a shared pair of electrons attracted to the nuclei of bonded atoms. |
| bond polarity/bɒnd pəʊˈlærɪti/ | bond polarity |
The tug-of-war for electrons
- Electronegativity 电负性 is an atom's power to attract the electrons in a bond towards itself.
- It follows a clear trend across the Periodic Table.
- The difference between two atoms tells you the bond type.
The power of an atom to attract the electrons in a covalent bond is its ______.
Difficulty 1/5 · 100 coins + a small bonus on first completion today
It increases across a period and up a group (fluorine is the highest).
Electronegativity is:
Difficulty 1/5 · 100 coins + a small bonus on first completion today
Electronegativity measures how strongly an atom pulls the shared bonding electrons towards it.
What sets it, and the trend
- Three factors: nuclear charge 核电荷 (more protons → stronger pull), atomic radius (closer → stronger), shielding (more inner electrons → weaker).
- So it rises across a period and falls down a group.
- Fluorine is the most electronegative element.
Sharing a pair of electrons
Step through a covalent bond: two atoms overlap and share a pair so each reaches a full shell — when the two pull equally the bond is non-polar.
Electronegativity:
Difficulty 1/5 · 100 coins + a small bonus on first completion today
More nuclear charge and smaller radius across a period raise it; more shells down a group lower it. F is the highest.
Which change increases an atom's electronegativity?
Difficulty 1/5 · 100 coins + a small bonus on first completion today
More protons (nuclear charge) pull the bonding electrons more strongly; radius and shielding lower it.
Electronegativity falls across a period and rises down a group, so caesium is the most electronegative element.
Difficulty 1/5 · 100 coins + a small bonus on first completion today
False. Electronegativity rises across a period (smaller radius, more nuclear charge) and falls down a group (more shells), so fluorine is the most electronegative element.
Predicting the bond type
- A large electronegativity difference → an ionic bond 离子键.
- A small difference → a covalent bond 共价键.
- (We compare Pauling electronegativity values.)
A large electronegativity difference between two atoms gives:
Difficulty 1/5 · 100 coins + a small bonus on first completion today
A big difference means electrons are transferred (ionic); a small difference means they are shared (covalent).
Match each electronegativity difference to the bond it gives.
Difficulty 2/5 · 140 coins + a small bonus on first completion today
The bigger the electronegativity gap, the more the electrons shift — from shared (covalent) to fully transferred (ionic).
Trends in electronegativity
- Electronegativity increases across a period and decreases down a group.
- Fluorine is the most electronegative element; the trend predicts bond polarity 键的极性.
Electronegativity rises across a period and falls down a group — fluorine is the highest.
You've got it
- electronegativity = power to attract bonding electrons
- set by nuclear charge, radius, shielding; rises across, falls down; F is highest
- large difference → ionic; small → covalent