L2: Bonding Between Atoms And Molecules

Question 1

Define electropositive and say where electropositive elements are?

Answer 1

To the left of the table

Very few electrons in their outer shell and removing them is fairly easy- low IE)

Question 2

Define Electronegative and say where you’d find electronegative elements of the table?

Answer 2

To the right of the table (not the noble gasses tho)

Have many electrons in outer shell, prefer to gain extra electrons to fill shell

Question 3

What is valency related to? What does it indicate?

Answer 3

Chem combination with other elements
# of electrons in outer orbitals

Indicates the ratios in which atoms will combine to form a molecule, eg AlCl3

Question 4

What is the typical valency of each group in the table (1-8)

Answer 4

1- 1
2-2
3-3
4-4
5-3
6-2
7-1

Question 5

Describe primary bonding and give the 3 examples

Answer 5

Strong Chem interactions between atoms

Electrons shared/ transferred between atoms

Question 6

Describe secondary bonding and give 2 egs

Answer 6

Weak interactions between atoms and/ or molecules (electrons remain with parent atoms)

Van see waals
Hydrogen bonding

Question 7

Describe ionic bonding

Answer 7

Metal + non metal from opposite ends of table
Electropositive loses an electron and becomes +ve
Electronegative gains an electron and becomes -ve

Ions held in 3d lattice to maximise interactions, held together by electrostatic attraction between +ve and -ve

Question 8

Give the 4 general properties of ionic materials

Answer 8

High mp/bp
High hardness
High Ym (stiffness)
High degree of brittleness

Question 9

Describe covalent bonding

Answer 9

Atoms share electrons which are held between the 2 nuclei forming molecules/solids
Bonds are directional- make shapes
#electrons shared depends on- atom bonding configuration

Question 10

What is covalent bonding important for?

Answer 10

Polymers

Question 11

If all bonds between atoms are covalent, what are its properties usually?

Answer 11

High Ym (stiffness)
Often brittle
High mp/bp

Question 12

Describe metallic bonding

Answer 12

Sharing of valence electrons between all atoms present
Electrons are considered to be disconnected from the atoms and free to move anywhere
Leads to electrical conductivity
Electrostatic attraction between electron cloud and metal ions holds metal together

Question 13

Properties of metallic bonding?

Answer 13

Good tensile and compressive strength

High ductility

Question 14

Define ductility

Answer 14

A measure of how much a material can be plastically deformed

Question 15

Describe secondary bonding

Answer 15

Take place between atoms/ molecules
Weak but play significant role in material properties (eg h20 and polymers)
No transfer/electron sharing

Question 16

Describe Van der Waals forces

Answer 16

Electrons repel eachother when atoms approach, distorting the charges forming a dipole.
Overall attraction outweighs repulsion but not by much so weak forces occur holding atoms together
Sometimes happens with permanent dipoles

Question 17

Examples of van der waals substances (2)

Answer 17

Holds atoms in solid and liquid He (bp 4K)

Holds Ni molecules in solid and liquid Nitrogen (bp 77k)

Question 18

What atoms do hydrogen bonds form with?

Answer 18

H-F
H-O
H-N