[5.3] covalent bonding

Question 1

what is a covalent bond?

Answer 1

a covalent bond is the strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 2

where does covalent bonding occur?

Answer 2

• non-metallic elements (eg O=O)
• compounds of non-metallic elements (eg. water)
• molecular ions

Question 3

what kinds of covalent bonds are there? (3)

Answer 3

• single
• multiple
• dative

Question 4

what is a better rule than the octet rule? (that there are only 8 electrons to be bonded in a shell)

Answer 4

• unpaired electrons pair up
• the maximum number of electrons that can pair up is equivalent to the number of electrons in the outer shell

Question 5

how can molecule phosphorus pentachloride have 10 electrons in its outer shell?

Answer 5

• phosphorus can pair up with 5 electrons so this is what it does
• also phosphorus is in period 3, which means it can hold 18 electrons in its outer shell
  > this is called expanding the octet

Question 6

what is a dative or coordinate covalent bond?

Answer 6

a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only

Question 7

how do you show a dative covalent bond in the displayed formula?

Answer 7

with an arrow, which points from the atoms which provides a bonded pair towards the one without a bonded pair

Question 8

what is average bond enthalphy?

Answer 8

average bond enthalphy serves as a measurement of covalent bond strength. the larger the value of the average bond enthalphy, the stronger the covalent bond