Covalent Bonding

Question 1

when is a covalent bond formed between two atoms

Answer 1

• when an atomic orbital containing one electron from one atom
• overlaps with the an atomic orbital containing a single electron from another atom

Question 2

how many different ways can s-orbitals overlap

Answer 2

one way

Question 3

how many different ways can p-orbitals overlap

Answer 3

two way

Question 4

what is the one way s orbitals can overlap

Answer 4

end on overlap (like a venn diagram)

Question 5

what are the two ways p orbitals can overlap

Answer 5

• end on overlap

- sideways overlap

Question 6

between end on and sideways overlaps, which ones create sigma and pi bonds

Answer 6

• end on overlaps create sigma bonds

- sideways overlaps create pi bonds

Question 7

why do the end on overlaps create sigma bonds

Answer 7

• with an end on overlap you only have one region of overlapping
• the s orbital is like a circle so it can only have one region of overlapping
• the p orbital is like an 8 shape, so it forms a single region of overlapping by only the top or bottom (the ends) overlapping
• creating a sigma (single) bond

Question 8

why do sideways overlaps create pi bonds

Answer 8

• if the p orbitals overlap the ‘right way up / sideways’ (8) there will be two regions of overlapping
• creating the pi bond

Question 9

using the idea of orbitals, how is a hydrogen molecule formed

Answer 9

• the two hydrogen atoms have one electron in their 1s orbital
• the two s orbitals simply overlap to form a new molecular orbital
• the two electrons then exist in this new orbital, creating the sigma bond

Question 10

using the idea of orbitals, how is a chlorine molecule formed

Answer 10

• chlorine has one electron in one of its p orbitals (as it has 3 in the p subshell)
• these p orbitals undergo end on overlap to form the sigma bond

Question 11

what condition firstly has to be met in order for a pi (double) bond to form

Answer 11

a sigma bond already needs to be present

Question 12

what does the sideways overlap of p orbitals creating a pi bond cause for the molecule

Answer 12

a high electron density both above and below it

Question 13

why are pi bonds weaker than sigma bonds

Answer 13

• because they are further away form the atoms which are having their p orbitals overlapping sideways
• meaning the electrons in the pi bonds experience less electrostatic attraction from them
• making a less stable and therefore weaker bond

Question 14

what does the triple bond in the nitrogen molecule consist of

Answer 14

one sigma bond and two pi bonds

Question 15

what is the definition of bond length

Answer 15

• the distance between the nuclei of the two atoms

- that are covelantly bonded together

Question 16

what is the strength of a covelant bond determined by

Answer 16

the amount of energy required to break one mole of the bond in a gaseous state

Question 17

what is the general relationship between bond length and bond strength for bonds that are similar in nature

Answer 17

the shorter the bond, the stronger the bond

Question 18

why does a shorter bond result in greater bond strength

Answer 18

• if the bond is shorter it means the electrons making the bond are closer to the two nuclei
• this results in stronger electrostatic forces of attraction between them
• making it harder to separate them

Question 19

what is the relationship between the number of bonds two atoms have and their bond strength and why

Answer 19

• an increase in the number of bonds leads to stronger bonds

- because the bond length decreases as the number of bonds increases