(U1) Bonding

Question 1

What is a covalent bond? (3)

Answer 1

• electrostatic attraction
• between a shared pair of electrons
• and the nuclei of bonded atoms

Question 2

What is a lone pair? (2)

Answer 2

• a pair of unshared electrons
• in the outer shell

Question 3

What is a co-ordinate / dative bond? (3)

Answer 3

• a shared pair of electrons
• between 2 atoms
• 1 atom provides both electrons

Question 4

State the octet rule (3)

Answer 4

• when forming a compound
• an atom tends to gain, lose or share electrons
• to achieve 8 in its outer shell and become stable

Question 5

What is electronegativity? (2)

Answer 5

• the extent to which an atom attracts bonding electrons
• in a covalent bond

Question 6

What is a polar bond? (3)

Answer 6

• a covalent bond
• with unequal sharing of the bonding electrons
• caused by atoms having different electronegativities

Question 7

What are delocalised electrons? (2)

Answer 7

• outer electrons
• with no fixed positions and that move freely

Question 8

What is an Ionic bond (3)

And

What does it bond?

Answer 8

• electrostatic attraction
• between oppositely charged ions
• formed by electron transfer

2. Metals and non-metals

Question 9

How do you represent a dative bond in a diagram?

Answer 9

An arrow from the atom donating a lone pair of electrons to the ion

Question 10

What is the most electronegative element?

Answer 10

Fluorine

Question 11

What difference value on the Pauling scale results in a:

• pure covalent
• polar covalent
• ionic bond?

Answer 11

• 0 = pure
• 0-1.7 = polar
• more than 1.7 = ionic

Question 12

Name 3 contradictions to the octet rule

Answer 12

• BeCl₂
• BF₃
• AlCl₃

Question 13

Name an expansion to the octet rule

Answer 13

SF₆

Question 14

Why does BeCl₂ contradict and follow the octet rule? (2)

Answer 14

• Be atom has 4 outer shell electrons - doesn’t follow
• Cl atom has 8 outer shell electrons - does follow

Question 15

What factors influence m.p. And b.p.? (3)

not including intermolecular forces

Answer 15

• atomic radius: increase = decreased m.p./b.p.
• nuclear charge: increase = increased m.p./b.p.
• shielding by inner electrons: increase = decreased m.p./b.p.

Question 16

What is the general trend in electronegativity down a group?

Why? (3)

Answer 16

electronegativity decreases:

• increased atomic radius
• greater shielding
• as a result bonding electrons are further from the nucleus and the electrostatic attraction is decreased

Question 17

What is the general trend in electronegativity across a period?

Why? (3)

Answer 17

Electronegativity increases:

• greater nuclear charge of atoms
• smaller atomic radius
• therefore electrostatic attraction is increased and the outer electrons are more attracted to the nucleus

Question 18

What is a metallic bond? (2)

Answer 18

• The electrostatic attraction between a metallic cation
• and delocalised electrons in a lattice