Shapes Of Molecules

Question 1

Which electron pairs determine the shape of the molecule?

Answer 1

Both bonding and lone pairs of electrons determine the shape of the molecule.

Question 2

What equation can we use to find out how many electron pairs are around a central atom in a given molecule?

Answer 2

Group number + number of atoms attached to it - charge / 2

Question 3

Which electron pairs occupy more space, Lone or bonding?

Answer 3

Lone pairs occupy more space in an atom.

Question 4

Draw the trigonal planar shape. How many bonding pairs? What is the bond angle?

Answer 4

120 degrees 3 bonding pairs

Question 5

Draw the square planar shape. What is special about the bond angle here?

Answer 5

The bond angle doesn’t change because the lone pairs repel each other in equal and opposite directions. So it is still 90 degrees.

Question 6

What is the VSEPR theory?

Answer 6

The theory that the valence electron pairs arrange themselves around the central atom to remain at a maximum distance apart to keep repulsion at a minimum.

Question 7

What is the shape of a PCl,5 molecule and what are the bond angles?

Answer 7

5+5/2=5 Trigonal bipyramid shape Bond angles of 120 and 90 degrees.

Question 8

Work out the shape of the following molecules and state bond angles: 1) SF,6 2) XeF,4 3) PH,3 4) CH,4

Answer 8

1) octahedral - 90 degrees 2) square planar - 90 degrees 3) trigonal pyramidal - 107 degrees 4) tetrahedral - 109.5 degrees

Question 9

How do lone pairs affect the bond angle?

Answer 9

Bond angles are reduced by 2.5 degrees with every lone pair of electrons. E.g. 109.5 - 2.5 = 107 degrees

Question 10

What is the name of the shape of a molecule with 2 bonding pairs?

Answer 10

Linear

Question 11

What is he name of that has 2 bonding pairs and 1 lone pair?

Answer 11

Bent/ v-shaped

Question 12

Draw the trigonal pyramidal shape and state the bond angle.

Answer 12

Bond angle - 107 degrees

Question 13

Explain the shape and bond angle in NH,3.

Answer 13

Nitrogen has 5 electrons in its outer shell. Each hydrogen shares 1 electron with nitrogen so there’s 8 electrons in total, so there’s 4 pairs of electrons. There are 3 bonding pairs and 1 lone pair. Electron pairs repel as far as possible. Lone pairs repel more than bonding pairs. So it is a trigonal pyramidal shape. The bond angle is 109.5 reduced to 107 degrees.

Question 14

What is the equation of oxygen is attached to the central atom?

Answer 14

Group number - charge /2 E.g. CO,2 4/2 = 2 So a linear shape O=C=O