Atomic Bonding

Question 1

Matter is divided into?

Answer 1

Mixture and Pure Substance

Question 2

Describe bonding in molecules:

Answer 2

Molecules have primary bonds within the molecule and secondary bonds between molecules

Question 3

Define solid

Answer 3

“Solids” (for our purposes) have primary bonds between all atoms in the substance so that a crystal or 3D network
exists

Question 4

Three primary bonds?

Answer 4

• Ionic
• Metallic
• Covalent

Question 5

2 secondary bonds?

Answer 5

• Van der waals
• Hydrogen

Question 6

Threshold electronegativity for ionic bonds? (Difference in electronegativity)

Answer 6

> 1.7

Question 7

For electronegativity below 1.7, of the average electronegativity is high, what bond is it?

Answer 7

Covalent as outer shell is almost filled

Question 8

For electronegativity below 1.7, of the average electronegativity is low, what bond is it?

Answer 8

Metallic and outer shell is nearly empty

Question 9

What is ‘no directionality’ and which bonding is associated with it?

Answer 9

Radically symmetric. Thus can from a number of different crystall structures

Apart of ionic bonding

Question 10

Metallic bonding properties:

Answer 10

• Zero or low electronegativity difference.
• Outer shell usually less than half full.
• The few electrons in the outer shell are not enough to fill the shells of two atoms if shared. They must be
  shared between all the atoms in the material.
• The electrons are delocalised
  and freely move around all the
  nuclei.
• The result is high electrical
  and thermal conductivity.

Question 11

How do we get force from a well gragh?

Answer 11

Derivate of energy with respect to distance

Question 12

The amount of energy to separate molecules or atoms is equivalent to?

Answer 12

The vertical distance from distance axis to tipping point

Question 13

At what position is the energy at absolute zero (K=0)

Answer 13

Tipping point

Question 14

Boling point trends as chain length decreases and why for alkanes:

Answer 14

Boiling temperature of alkanes (molecular liquids) decreases as chain length
decreases because van der Waals interactions decrease for smaller molecules

Question 15

Yield Stress is?

Answer 15

The stress required to permanently (plastically) deform a material.

Question 16

Elastic deformation is?

Answer 16

The material deforms under stress then springs back to its original shape when stress
is removed.

Question 17

The coefficient of thermal expansion (CTE) is?

Answer 17

Materials usually expand as they are heated up

Question 18

The maximum force to separate two atoms is equivalent to?

Answer 18

Yield strength

sigma = F * number of bonds per unit area

Question 19

Elastic Modulus is?

Answer 19

a measure of how much deformation will occur for a given applied stress
(force). Atoms are pulled apart (or pushed together) slightly when a stress is applied.

Question 20

Relation to hooke’s law and elastic modulus?

Answer 20

– Force between atoms is analogous
to the restoring force of a force spring atom spring in Hooke’s Law

• F=kD=kd

Question 21

Modulus characteristics from gragh:

Answer 21

Sharp curvature = high modulus
Shallow curvature = low modulus

generally deeper wells (stronger bonding) will have sharper curvature.