Lecture 2

Question 1

How do bonds impact things like boiling and melting point?

Answer 1

In bonds, the number of them, their type, strength and direction can impact properties like boiling and melting point.

Stronger bonds -> higher melting point as stronger bonds must be broken

and vice versa

Question 2

What is valency?

Answer 2

When an element reacts, it attempts to achieve a full outer electron shell by losing, gaining or sharing electrons.

Elements on the left of the periodic table are said to be electropositive. They have few electrons in their outer shell which can be removed easily (low ionisation energy)

Elements on the right of the periodic table are said to be electronegative (excluding noble gases). They tend to gain electrons to fill their outer shell rather than losing them.

Valency is used to indicate the ratios atoms will combine with each other to form a molecule or solid (NaCl, CO2 etc.)

Question 3

What is the valency of each group in the periodic table?

Answer 3

1: 1, are very reactive and tend to lose their electron to form ions.

2: 2, reactive and tend to lose both electrons to form ions

3: 3, quite reactive and may form ionic, covalent or metallic bonds depending on the elements

4: 4, do not form ions and mostly share electrons through covalent bonds

5: 3, prefer to share/gain electrons to complete the outer shell

6: 2, prefer to share/gain electrons to complete the outer shell

7: 1, very reactive, can form ionic or covalent bonds to complete the outer shell

8: Noble gases with complete outer shells that are very unreactive

Question 4

What are the interactions between atoms and molecules?

Answer 4

A number (2 or more) of atoms can come together to form molecules, which then form solids.

Atoms -> molecules -> solid composed of molecules

Large numbers of atoms (or ions) come together to form solids.

Atoms (or ions) -> solid composed of atoms (or ions)

Question 5

What are the Classes of Bonding?

Answer 5

The nature of the bonds between atoms and molecules affects materials properties.

Primary: Strong chemical interactions between atoms where electrons are shared or transferred (Ionic, Covalent, Metallic)

Secondary: Weak interactions between atoms and/or molecules
where electrons remain with parent atoms (Van der Waals, Hydrogen Bonding)

Question 6

What are Primary Bonds?

Answer 6

Ionic Bonding, transfer of electrons from one atom to another where ions are created. Generally between metals and non-metals from opposite ends of the periodic table.