Chemistry IGCSE Aid Chapter 4

Questions and Answers

What are valence electrons?

Valence electrons are the number of electrons in an atom's outer shell.

What is valency?

Valency is the number of electrons an atom needs to gain or lose to become stable.

For groups I to IV, the valency is the same as the ______ no.

group

Match the following groups with their respective valency:

Group I = +1 Group II = +2 Group III = +3 Group IV = -4 Group V = -3 Group VI = -2 Group VII = -1 Group 0 = 0 Signup and view all the answers

What is the formula for Magnesium Chloride?

MgCl2 Signup and view all the answers

What comes first in a metal and a non-metal compound?

The metal's symbol. Signup and view all the answers

Which of the following compounds contains hydrogen?

Sodium Hydroxide Signup and view all the answers

What is the chemical formula for Sodium Hydroxide?

NaOH Signup and view all the answers

What is the chemical formula for Magnesium Nitrate?

Mg(NO3)2 Signup and view all the answers

What is the chemical formula for Calcium Sulfate?

CaSO4 Signup and view all the answers

What is the chemical formula for Sodium Carbonate?

Na2CO3 Signup and view all the answers

In an ionic compound, the number of positive charges is equal to the number of negative charges.

True Signup and view all the answers

Study Notes

Valence Electrons and Valency

Valence electrons are the electrons in the outer shell of an atom, crucial for bonding.
Valency indicates how many electrons an atom must gain or lose to achieve stability.

Determining Valency

For groups I to IV, valency equals the group number and the number of valence electrons.
For groups V to 0, the valency is calculated as 8 minus the group number.
Valencies correspond as follows:
- Group 1: +1
- Group 2: +2
- Group 3: +3
- Group 4: -4
- Group 5: -3
- Group 6: -2
- Group 7: -1
- Group 0: 0

Magnesium Chloride Example

Magnesium (Mg) is in Group II, with a valency of 2; Chlorine (Cl) is in Group VII, with a valency of 1.
The formula writing involves:
- Symbols: Mg Cl
- Valencies: Mg2 Cl1
- Swapping: Mg1 Cl2
- Simplifying gives the final formula: MgCl2.

Compound Naming Rules

For compounds with a metal and a non-metal, the metal's symbol precedes the non-metal, which ends with -ide.
In hydrogen-containing compounds, hydrogen is listed first.
When two non-metals are involved, the one from the lower group number comes first. If both are in the same group, the lower one is listed.

Common Compound Formulas

Sodium Hydroxide: NaOH
Magnesium Nitrate: Mg(NO3)2
Calcium Sulfate: CaSO4
Sodium Carbonate: Na2CO3

Ionic Compounds and Charge Balance

In ionic compounds, the total positive charges balance the total negative charges.
Charge information is derived from the valences of the elements involved.

Description

This quiz focuses on key concepts from Chapter 4 of the IGCSE Chemistry curriculum. It includes important terminology related to valence electrons and valency, providing a solid foundation for understanding chemical bonding. Use these flashcards to test your knowledge and prepare effectively for your chemistry exams.