Chemical Bonding

Question 1

Ionic Bonding:

Answer 1

• Occurs between atoms with large differences in their
  tendencies to lose or gain electrons (large ∆EN)
• Transfer of electrons from metal atoms to nonmetal
  atoms to form ions that attract each other and form a
  solid ionic compound.

Question 2

Ionisation Energy

Answer 2

Ease that atom gives up an e

Question 3

Electron affinity

Answer 3

Amount of energy released when an e is added

Question 4

Important

Answer 4

Electrostatic attraction is the main contributor in Ionic bonding

Question 5

Lattice energy

Answer 5

enthalpy change required to separate 1 mol of ionic solid into its gaseous ions (NaCl -> Na+ + Cl-)

Question 6

Hess’s Law

Answer 6

the enthalpy change of an overall reaction is the sum of the enthalpy changes for the individual reactions that make it up.
AND
enthalpy in a chemical reaction is independent of
the pathway between the initial and final states.

Question 7

Physical Properties of Ionic Compounds

Answer 7

• Hard (Does not bend).
• Rigid.
• Brittle (cracks without deforming).
• Typically soluble in water (although there are a few
  exceptions – look up solubility rules).

Question 8

Electrical conductivity

Answer 8

• Non-conducting solids (‘flow’ of charge required).
• Conducts electricity either when molten or dissolved

Question 9

Melting and boiling points

Answer 9

• Large amount of energy required to separate ions (recall lattice energy), therefore high melting point and much higher boiling point.

Question 10

Covalent Bonding

Answer 10

• A covalent bond involves the sharing of electrons between two atoms such that there is a balance between all attractive and repulsive forces between the atoms.

Question 11

Bond Energy (Bond strength)

Answer 11

The energy required to overcome attractive forces in a covalent bond (Don’t confuse with the energy of molecule!!).

Question 12

Bond Length

Answer 12

Distance between two nuclei of bonded atoms.

Question 13

Behaviour of covalent bonds

Answer 13

• Poor conductors of electricity
  -no ions or mobile electrons, even when dissolved in water.
• Low melting and boiling points.

Question 14

BUT COVALENT BONDS ARE
STRONG, SO WHY???

Answer 14

Weak forces between molecules. Unlike ionic compounds
whose lattice energy is very high and therefore require
more energy to affect physical properties.

Question 15

Electronegativity

Answer 15

• Electronegativity (EN) is the relative ability of a bonded
  atom to attract shared electrons.
  NOTE: Electron affinity (EA) is the actual transfer. While EN is a “polarisation effect”.

Question 16

Electronegativity Trends

Answer 16

• Increases across a period.
• Decreases down a group.

Question 17

Predicting Bonding Type

Answer 17

A greater EN results in larger partial charges and a higher partial ionic character

Question 18

Metallic Bonding

Answer 18

• Recall physical properties of ionic bonding:
• Metals don’t crack, rather they deform.

Question 19

Electron-Sea Model

Answer 19

• The electron-sea model proposes that all metals in the sample contribute their valence electrons to form a delocalised electron “sea” throughout the sample, with the metal core (nuclei and core electrons) lying in an orderly array. All the metal atoms in the sample share the electrons.