The diagram below shows a representation of the structure of an ionic oxide. What is the ratio of K + ions to O 2- ions? _____ .

The ratio of K + ions to O 2- ions is 2 : 1 . When potassium combines with oxygen, it forms potassium oxide(K 2 O). Metal oxides are crystalline solids that contain a metal cation and an oxide anion. They typically react with water to form bases or with acids to form salts.

The diagram below shows a representation of the structure of an ionic oxide. What is the formula of this compound?

The formula of the compound is K 2 O .It is a base. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound. It is deliquescent and will absorb water from the atmosphere, initiating this vigorous reaction.

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

Graphite is one of the crystalline forms of carbon. Two of the distinctive properties of graphite are:

It conducts electricity even though it is a non-metal, and

It can act as a lubricant even though it has a giant covalent structure.
Give a brief explanation of these properties in light of the structure of graphite.

Graphite are as lubricant.

Important Questions on Elements and Compounds

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.5>Q c

The diagram below shows a representation of the structure of an ionic oxide.
Question Image

What is the ratio of K⁺ ions to O^2-ions? _____ .

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.5>Q c

The diagram below shows a representation of the structure of an ionic oxide.
Question Image
What is the formula of this compound?

HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.5>Q d

The following diagram shows the structure of common salt.
Extend the structure to the right, by adding four more ions.
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HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.5>Q d

Complete the diagrams below for the ions in the structure to show their electron arrangement. Draw in any missing electron shells, showing clearly the origin of the electrons involved.
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HARD

Upper Secondary-IGCSE

IMPORTANT

Cambridge IGCSE Chemistry Workbook 4th Edition>Chapter 3 - Elements and Compounds>Exercise 3.5>Q d

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

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.

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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.

Important Questions on Elements and Compounds

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