Chapter 6

Question 1

What is the VSEPR theory?

Answer 1

VSEPR theory says that all electrons are negative so electron pairs repel and the amount repulsion determines the angles of the bonds and that’s the shape of the molecule

Question 2

Do bonding pairs or lone pairs have the largest repulsion?

Answer 2

Lone pairs have the largest repulsion

Question 3

When drawing molecules what do a straight line a shaded wedge a non shaded wedge

Answer 3

A struggle line means a bond in the plane
A shaded wedge means a bond coming out of the plane
A non shaded wedge means a blonde going into the plane

Question 4

What is the Shape and angles of a molecule with two bonded electron pairs?

Answer 4

It has a linear shape and 180° angles

Question 5

What is the shape and angles of a molecule with three bonded electron pairs?

Answer 5

It has a Trigano planar shapeAnd 120° angles

Question 6

What is the shapes and angles of a molecule with for bonded pairs of electrons?

Answer 6

It has a tetrahedral shape and 109.5° angles

Question 7

What is the shape and angles of a molecule with three bonded pairs of electrons and one lone pair of electrons?

Answer 7

It has a triagonal pyramidal shape and 107° bonds

Question 8

What is the shape and angles of a molecule with two bonded and two lone pairs of electrons?

Answer 8

It has a non-linear shape and 104.5° angles

Question 9

What is the shape and angles of a molecule with five bonded pairs of electrons?

Answer 9

It has a triagonal bipyramidal shape and also 90 and 120° bonds

Question 10

What is the shape and angles in a molecule with six bonded pairs of electrons?

Answer 10

Has octahedral shape and 90° bonds

Question 11

Definition of electronegativity

Answer 11

Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond

Question 12

What is electronegativity based on?

Answer 12

Electronegativity is based on nuclear charge, atomic radius and shielding

Question 13

In what direction does electronegativity increase in the periodic table?

Answer 13

Electronegativity increases towards fluorine in the periodic table

Question 14

What is Pauling scale?

Answer 14

Paulings scale displays all electronegativity values

Question 15

What is a polar bond?

Answer 15

A polar bond is a bond that occurs when there is a difference in electronegativity between the atoms in a covalent bond to the bonding electrons are pulled towards a more electronegative atom making it slightly more negative causing a permanent dipole

Question 16

What is a dipole?

Answer 16

A dipole is a difference in charge due to a shift in the electron density

Question 17

So what is a polar molecule?

Answer 17

Polar molecule is a molecule where the charge is arranged unevenly so the molecule have an overall dipole

Question 18

Is a molecule that has polar bonds always a polar molecule?What cases would it not be

Answer 18

If the polar bonds are symmetrical the dipoles cancel each other out there is no overall dipole and the molecule is nonpolar

Question 19

Name the first type of intermolecular force

Answer 19

London forces – are induced dipole dipole interactions between all atoms and molecules caused by the constant random movement of electrons towards or away from the nuclei which create temporary dipoles

Question 20

When are London forces stronger?

Answer 20

London forced are stronger when the atom has more electrons

Question 21

Name the second type of intermolecular force

Answer 21

Permanent dipole dipole interactions- The Delta plus and Delta minus charges and polar molecules cause week electrostatic forces between molecules

Question 22

Name the third type of Intermolecular forces

Answer 22

Hydrogen bonding – only occurs when hydrogen is covalently bonded to fluorine, nitrogen oxygen because hydrogen is so small and they are so electronegative the bond is so polarised a weak bond forms

Question 23

Why is solid ice less dense than water?

Answer 23

Water molecules have 2 bonded and 2 line pairs allowing it to form four hydrogen bonds Which hold water molecules apart in an open lattice structure. They are held further apart in ice than water as when it melts the lattice collapses so ice is less dense.

Question 24

Why does water have relatively high melting and boiling points?

Answer 24

Hydrogen bonds needs a lot of energy to overcome the electrostatic forces of attraction

Question 25

What is a simple molecular lattice?

Answer 25

A simple molecular lattice is made up of simple molecules (iodine, ice) the molecules are held in place by weak intermolecular forces and the atoms within each molecule are held by covelant bonds.

Question 26

What are the properties of simple molecular substances and why

Answer 26

• Low Melting and boiling points as the week into molecular forces can be broken by low energy
• solubility- soluble Iin non polar solvents as forces form between the molecule and the solvent weakening those in the lattice
  Insoluble in polar solvents as the bonding in polar solvents is too strong to be broken
• non conductors - no mobile charged particles

Question 27

What is a simple molecule ?

Answer 27

small units containing a definite number of atoms with a definite formula