1.3 - Bonding Flashcards
Covalent Bond Defintion
The electrostatic attraction between a shared pair of electrons and the nuclei of bonded atoms.
Lone Pair
A pair of unshared electrons in the outer shell of an atom.
Co-ordinate (Dative) Bond Definition
Give an example of a co-ordinate (dative) bond.
A shared pair of electrons between two atoms. One atom provides both electrons.
Ammonium ion, NH4+
Octet Rule Definition
When reacting, an atom tends to gain, lose or share electrons to achieve eight in its outer shell.
Electronegativity Definition
The extent to which an atom attracts the bonding electrons in a covalent bond.
Polar Bond Definition
A covalent bond in which there is unequal sharing of the bonding electrons.
Delocalised Electrons Definition
Outer electrons do not have fixed positions but move freely.
What is ionic bonding?
Ionic bonding is the electrostatic attraction between oppositely charged ions formed by electron transfer. Ionic bonding occurs between metal and non-metal atoms.
Give the names of some compounds where the octet rule does not apply.
BeCl2
BF3
Why do some covalent compounds deviate from the octet rule?
The elements involved in this arrangement are usually found at the top or second from the top in a group on the periodic table. The valence electrons in these atoms are close to the nucleus and are therefore held tightly (high IE, ionisation energy), hence sharing electrons is more feasible than complete electron transfer.
What is the trend in electronegativity across a period?
As you go across a period the electronegativity increases.
What is the trend in electronegativity down a group
As you go down a group electronegativity decreases.
How does bond polarity arise?
Bond polarity arises when covalently bonded atoms have different electronegativities.
Why does electronegativity increase as you go across a period?
Electronegativity increases across a period:
• Due to an increase in nuclear charge
• Due to a decrease in atomic radius
• Due to a decrease in distance between the electrons and the nucleus
Why does electronegativity decrease as you go down a group?
Electronegativity falls as you go down a group:
• Due to an increase in the number of shielding electrons
• Due to an increase in atomic radius
• Due to an increase in the distance between the electrons and the nucleus.
