Structure of Biological Macromolecules

Question 1

What is Matter?

Answer 1

Anything that has mass and occupies space, things you can see, touch, taste and smell

Question 2

What is the difference between the atomic mass and the atomic number?

Answer 2

atomic mass = the number of protons and neutrons

atomic number = the number of protons

Question 3

What is an isotope and how do they act?

Answer 3

the same elements with different atomic masses, they act the same as the normal atom

Question 4

Why do elements found in the same group have similar chemical properties?

Answer 4

As they have the same number of valence electrons, as it is these electrons which bond with other atoms and play a role in reactions it causes similar chemical properties

Question 5

What is the difference between a covalent and an ionic bond, and why does this occur?

Answer 5

A covalent bond is the sharing of electrons and an ionic bond is the transfer of electrons

Atoms do this in order to fulfil their outer shell configuration and gain a noble gas configuration

Question 6

How is the type of bonding in a molecule determined?

Answer 6

Through the molecules electronegativity difference

• above 2.0 = ionic
• between 0.4 and 2.0 = polar covalent
• under 0.4 = non polar covalent

Question 7

When does a covalent bond form?

Answer 7

When electron orbitals overlap

Question 8

What is Hybridisation?

Answer 8

the concept of mixing atomic orbitals in order to create new hybrid orbitals suitable for the pairing of electrons to form chemical bonds

Question 9

What rule must covalent bonding satisfy?

Answer 9

The octet rule (8 electrons in the valence shell)

Question 10

What are the steps in drawing a lewis structure?

Answer 10

1. Draw the skeleton along with the central atom
2. Determine the number of valence electrons in the molecule
3. Put the electrons into the structure
4. Determine how many electrons are needed to fill the octets
5. Place in lone electrons

Question 11

Can molecules have more than one lewis structure?

Answer 11

yes. This exists for structures with alternate single-double bond arrangements

Question 12

What occurs in resonance hybrids?

Answer 12

The density of some electron pairs are delocalised (spread across the entire molecule)

Question 13

What are the different geometries of molecular shapes?

Answer 13

Linear - 180 degrees (2 lone pairs)
Trigonal Planar - 120 degrees (3 lone pairs)
Tetrahedral - 109.5 degrees (4 lone pairs)
Trigonal Bipyramid - 90/120 degrees (5 lone pairs)
Octahedral - 90 degrees (6 lone pairs)

Question 14

What is the theory behind the VSEPR model?

Answer 14

“each group of valence electrons around a central atom is located as far from the others as possible in order to minimise repulsion”

• it is a model used to predict molecular (geometry) shape

Question 15

How is the VSEPR model applied?

Answer 15

1. Draw a lewis structure of the molecule, and identify the atom whose geometry is of interest
2. Count the number of electron charge clouds surrounding the atom of interest
3. Predict the molecular shape by assuming that the charge clouds orient in space so that they are as far from each other as possible

Question 16

What are principle energy levels?

Answer 16

The shells in space which electrons are confined to.

Each shell can hold 2n^2 electrons, where n = the shell number

Question 17

How can electron orbitals and valence electrons be determined?

Answer 17

Using the 1s, 2s, 2p etc organisation system