Draw dot and cross structural diagram to represent the bonding in the following simple molecular compounds. In the dot and cross diagram, show only the outer shells of the atoms involved. Molecule Dot and Cross diagram Structure Ammonia NH 3 Water H 2 O Hydrogen chloride HCl Ethane C 2 H 6 Ethene C 2 H 4 Ethanol C 2 H 5 OH Ethanoic acid CH 3 COOH

When a molecule is formed from the covalent bond, such compounds are known as covalent compounds. These compounds share one or more pairs of valence electrons. The covalent compound is a result of two non-metals reacting with each other such that they are electrically neutral. They exhibit characteristic physical properties that include lower melting points and electrical conductivity compared to ionic compounds.

Below is a table of observations and explanations for diamond, graphite and silica. Complete the table by filling in the gaps. The first section of the table has been completed for you; the other sections are partially complete. Observation Explanation Diamond and silica are both very hard substances _____ . _____ because all the atoms in the structure are joined by strong covalent bonds. Diamond does not conduct electricity _____ . _____ because Graphite is _____ . _____ because the layers in the structure are only held together by weak forces _____ because there are some free electrons that are able to move between the layers to carry the current.

Observation Explanation Diamond and silica are both very hard substances. Because all the atoms in the structure are joined by strong covalent bonds. Diamond does not conduct electricity. Because every atom in a diamond is bonded to its neighbours by four strong covalent bonds, leaving no free electrons and no ions . Graphite is lubricant . because the layers in the structure are only held together by weak forces Graphite conducts electricity . because there are some free electrons that are able to move between the layers to carry the current. Diamond and graphite are allotropes of carbon. The chemical formula for diamond and graphite is C. When diamond and graphite is heated , It burns with oxygen to form carbon dioxide.

HARD

Upper Secondary-IGCSE

IMPORTANT

Earn 100

Draw an ionic diagram similar to the one above for the structure of magnesium chloride.

Important Questions on Elements and Compounds

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.6>Q 1

Draw dot and cross structural diagram to represent the bonding in the following simple molecular compounds. In the dot and cross diagram, show only the outer shells of the atoms involved.

Molecule	Dot and Cross diagram	Structure
Ammonia $({NH}_{3})$
Water $(H_{2} O)$
Hydrogen chloride $(HCl)$
Ethane $(C_{2} H_{6})$
Ethene $(C_{2} H_{4})$
Ethanol $(C_{2} H_{5} OH)$
Ethanoic acid $({CH}_{3} COOH)$

MEDIUM

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.7>Q 1

The boxes below contain properties of ionic compounds and their explanations.Draw lines to link each pair.

Question Image

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.8>Q b

Below is a table of observations and explanations for diamond, graphite and silica. Complete the table by filling in the gaps. The first section of the table has been completed for you; the other sections are partially complete.

Observation	Explanation
Diamond and silica are both very hard substances _____ .	_____ because all the atoms in the structure are joined by strong covalent bonds.
Diamond does not conduct electricity _____ .	_____ because
Graphite is _____ .	_____ because the layers in the structure are only held together by weak forces
	_____ because there are some free electrons that are able to move between the layers to carry the current.

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.9>Q a

How does magnesium oxide depend on the starting mass of magnesium?

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.9>Q b

Work out from the graph the mass of the magnesium oxide that you would get from 0.12g of magnesium (show the lines you use for this on your graph) _____ g.

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.9>Q c

What mass of oxygen combines with

0.12

g of Magnesium? _____ g.

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.9>Q d

What mass of oxygen combines with

24

g of Magnesium? _____ g.

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.9>Q e

What is the molecular formula of magnesium oxide, worked out on the basis of these results? Relative atomic mass:

(Mg = 24, O = 16)

Draw an ionic diagram similar to the one above for the structure of magnesium chloride.

Important Questions on Elements and Compounds

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