Elements Of Life: Shapes of Molecules Flashcards
What is the shape of the molecules with
Total no. Areas = 2
Bond pair = 2
Lone pair = 0
Linear
Eg. BeCl 2
What is the shape of the molecules with
Total no. Areas = 3
Bond pair = 3
Lone pair = 0
Trigonal planar
eg. BF3
What is the shape of the molecules with
Total no. Areas = 4
Bond pair = 4
Lone pair = 0
Tetrahedral
Eg. CH4
What is the shape of the molecules with
Total no. Areas = 4
Bond pair = 3
Lone pair = 1
Trigonal pyramid
Eg. NH3
What is the shape of the molecules with
Total no. Areas = 4
Bond pair = 2
Lone pair = 2
Bent / V shaped
Eg. H2O
What is the shape of the molecules with
Total no. Areas = 5
Bond pair = 5
Lone pair = 0
Trigonal bypyramid
Eg. PF 5
What is the shape of the molecules with
Total no. Areas = 6
Bond pair = 6
Lone pair = 0
Octahedral
Eg. SF 6
What is the bond angle of a linear shape molecule
180°
What is the bond angle of a trigonal planar shape molecule
120°
What is the bond angle of a tetrahedral shape molecule
109.5°
What is the bond angle of a trigonal pyramid shape molecule
107°
What is the bond angle of a bent / v shapes shape molecule
104.5°
What is the bond angle of a trigonal bipyramid shape molecule
90° ( between 2 straight lines )
120° ( between dashes and wedge )
What is the bond angle of a octahedral shape molecule
90°
What is the electron repulsion theory (2)
- Electron pairs will repel each other as far as possible
- Shape of any molecule or ions is a consequence of the number of electron pairs which repel each other as far as possible
What is another name for an electron pair
Area of electrons
How do you work out the total no. of areas
No. of bond pairs + no. of lone pairs
Definition of bond pair
2 shares electrons in a covalent bond
Definition of love pairs
2 electrons in a pair not involved in bonding ( only counted it coming off the central atom )
What is special about double and triple bonds
Meant to consider them as 1 bonding pair
What does a lone pair do to a bonding angle and why
Reduce the bond angle by 2.5
- cos has a greater repulsion so pushes other atoms closer together
Give an example of when a lone pair changes the bond angle
In sulphur dioxide ( SO2 )
= 2 bonding pair
= 1 lone pair
Total = 3 therefore = trigonal planar but the 120° angle becomes becomes 117.5
( because 120 - 2.5 )
Give the electron repulsion theory for H2S
= 2 bonding pairs
= 2 lone pairs
Central S atom has 4 areas of electrons which repel as far as possible to give a bent shape
