bonding

Question 1

are metals made of ions or atoms?

Answer 1

• atoms
• there is a sea of delocalised electrons and positive metal ions
• but electrons have not been lost

Question 2

why is the metallic bond stronger in magnesium than sodium

Answer 2

• there are more delocalised electrons
• magnesium ions have a higher charge
• there is a stronger attraction between the delocalised electrons and positive metal ion
• also need to take into consideration charge density

Question 3

what is a metallic bond

Answer 3

• attraction between sea of delocalised electrons and the positive nucleus of metal ions

Question 4

what is a covalent bond

Answer 4

• attraction between the shared pair of electrons and the nucleus of the bonded atoms

Question 5

what determines the strength of a covalent bond

Answer 5

• size of the atoms

- the smaller the size, the shorter the covalent bond and so the stronger the covalent bond

Question 6

what is an ionic bond?

Answer 6

• electrostatic attraction between oppositely charged ions

Question 7

how do hydrogen bonds from?

Answer 7

• between the delta positive hydrogen on one molecule and a lone pair on either nitrogen, fluorine or oxygen which is also bonded to a delta positive hydrogen in a neighbouring molecule

Question 8

how many hydrogen bonds can each water molecule form and why?

Answer 8

• four
• the are exactly the same number of delta positive hydrogens and lone pairs so that each one of them are involved in hydrogen bonding

Question 9

how many hydrogen bonds can ammonia form and why

Answer 9

• two
• each ammonia molecule has one lone pair which isn’t enough to satisfy all the delta positive hydrogens
• on average, each ammonia molecule can form a hydrogen bond with one of the delta positive hydrogens and one with the lone pair
• the other delta positive hydrogens go to waste

Question 10

why does ice have a higher melting point than ammonia?

Answer 10

• ice has stronger hydrogen bonds because it forms twice as many hydrogen bonds as ammonia
• because the oxygen in ice has two lone pairs which can satisfy all the hydrogens
• but the nitrogen only has one lone pair which isn’t enough to satisfy all of the hydrogens

Question 11

what are the anomalous properties of water and why?

Answer 11

• high boiling point

- ice is less dense than water

Question 12

how does an induced dipole-dipole interaction form/ Van Der Waals’?

Answer 12

• at any instantaneous rate, there is an uneven distribution of electrons and there are more electrons on side of the molecule due to the constant movement of electrons
• this induces a temporary dipole
• this induces a temporary dipole on the neighbouring molecules
• the traction between these induced dipole are Van Der Waals’ forces