Electronegativity

Question 1

Define electronegativity

Answer 1

The power of an atom to attract electron density toward itself in a covalent bond

Question 2

Explain why electronegativity increases as you go across a period

Answer 2

• Same shielding
• ^ protons
• ^ nuclear charge
• stronger attraction between nucleus and electrons in the covalent bond
• a great deal of energy required to overcome

Question 3

Explain why electronegativity decreases as you go down a group

Answer 3

• ^ shielding
• ^ distance between nucleus and bonding pair of electrons
• weaker attraction between nucleus and electrons in the covalent bond
• less energy required to overcome

Question 4

Describe what is meant by a polar bond

Answer 4

• 2 atoms that bond have different electronegativity

Question 5

Describe what is meant by a non-polar bond

Answer 5

• 2 atoms that bond have the same electronegativity

Question 6

Describe what is meant by partial charges

Answer 6

• If the 2 atoms that bond together have different electronegatives (polar), this is represented by partial charges.
• The atom that is more electronegative has a partial negative charge, and the atom that is less electronegative has a partial positive charge

Question 7

Why can a molecule made up of several polar bonds be non-polar

Answer 7

• The molecules are symmetrical, thereforethere is no overall polarity

Question 8

What are the 3 intermolecular forces

Answer 8

• Van de Waals force (aka temporary or induced dipol)
• dipole-dipole forces
• hydrogen bonding

Question 9

Describe Van der Waals forces

Answer 9

• Weakest type of intermolecular force
• Present between all molecules
• Caused by the uneven distribution of electrons in an atom, which creates an instantaneous/temporary dipole
• This causes instantaneous induced dipoles in neighbouring molecules because of the attraction between oppositely charged partial charges

Question 10

Define dipole

Answer 10

• Molecules that have an uneven distribution of charge (polar)

Question 11

Describe permanent dipole-dipole forces

Answer 11

• occurs between molecules that possess an overall dipole charge (polar)
• opposite partial charges between the two molecules attract

Question 12

Explain the trend in boiling point of the noble gases, and link this to Van der waals forces

Answer 12

• As you go down the group, there are more electrons
• More electrons lead to more Van Der Waals forces
• Therefore a great deal of energy is required to overcome these forces

Question 13

Describe hydrogen bonding

Answer 13

• Strongest type of intermolecular force
• Occurs when a very electronegative atom (F,O,N) has a lone pair of electrons
• A hydrogen atom covalent my bonded to this electronegative atom

Question 14

Define lone pair

Answer 14

• A pair of outer electrons that are not involved in a bond

Question 15

Describe how to draw hydrogen bonds

Answer 15

• draw your molecules
• show any lone pairs or partial charges
• draw a straight dotted line between the lone pair on one atom and the hydrogen atom