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The Arrangement of Elements in the Modern Periodic Table of Elements

4.2 The Arrangement in the Periodic Table of Elements
CHEMISTRY • Form 4 • Chapter 4: The Periodic Table of Elements

4.2The Arrangement in the Periodic Table of Elements

The modern Periodic Table of Elements is a systematic classification of chemical elements arranged in ascending order of their proton numbers from left to right and from top to bottom. By knowing the proton number of an atom, its electron arrangement can be determined, which directly reveals its group and period in the Periodic Table.

Learning Objectives

  • Describe briefly the modern Periodic Table of Elements.
  • Generalise the relationship between the proton number and the position of elements in the Periodic Table of Elements (groups and periods).

Determining Group and Period from Electron Arrangement

Use the number of valence electrons and the number of filled shells to locate an element in the Periodic Table.

1
Write the electron arrangement from the proton number.
2a
Count the shells filled with electrons.
Period = number of shells filled with electrons
2b
Look at the valence electrons in the outermost shell.
1 or 2 valence electrons → Group 1 or 2
3 to 8 valence electrons → Group = valence electrons + 10

Brief Explanation

Understand how groups and periods are determined.

The modern Periodic Table of Elements arranges elements in ascending order of their proton numbers from left to right and from top to bottom.

Groups

Vertical columns in the Periodic Table are called Groups. There are 18 groups. The number of valence electrons determines the group of an element.

  • 1 or 2 valence electrons → Group 1 or 2.
  • 3 to 8 valence electrons → Group = valence electrons + 10.

Periods

Horizontal rows in the Periodic Table are called Periods. There are 7 periods. The number of shells filled with electrons determines the period of an element.

  • Period = number of shells filled with electrons.
Element Proton number Electron arrangement Valence electrons Group Period
Lithium, Li 3 2.1 1 1 2
Calcium, Ca 20 2.8.8.2 2 2 4
Aluminium, Al 13 2.8.3 3 13 3
Silicon, Si 14 2.8.4 4 14 3
Nitrogen, N 7 2.5 5 15 2
Oxygen, O 8 2.6 6 16 2
Bromine, Br 35 2.8.18.7 7 17 4
Krypton, Kr 36 2.8.18.8 8 18 4

Try to Answer First

Answer mentally, then check the explanation.

1

What determines the period of an element in the Periodic Table of Elements?

Answer: The number of shells filled with electrons.
2

An element has a proton number of 14. What is its group and period?

Answer: Its electron arrangement is 2.8.4. It has 4 valence electrons, so its group is 4 + 10 = 14. It has 3 shells filled with electrons, so its period is Period 3.
3

How are elements arranged in the modern Periodic Table of Elements?

Answer: In ascending order of proton numbers from left to right and from top to bottom.

Common Mistakes

Avoid these errors when determining the position of an element.

!
Forgetting to add 10 for elements with 3 to 8 valence electrons. For example, stating that aluminium is in Group 3 instead of Group 13.
!
Confusing groups with periods, such as taking the number of shells as the group and valence electrons as the period.
!
Using the nucleon number instead of the proton number to write the electron arrangement.

Concept Misunderstandings

Compare each misconception with the correct fact.

Misconception

Elements in the modern Periodic Table are arranged according to their relative atomic mass.

Correct Fact

In the modern Periodic Table, elements are arranged in ascending order of their proton numbers.

Misconception

All elements take their group number directly from the number of valence electrons.

Correct Fact

Only elements with 1 or 2 valence electrons have a group number equal to their valence electrons; elements with 3 to 8 valence electrons must add 10 to determine their group number (Groups 13 to 18).

Summary

Key facts to remember.

  • The modern Periodic Table arranges elements in ascending order of proton numbers.
  • Groups are the 18 vertical columns determined by the number of valence electrons.
  • 1 or 2 valence electrons → Group 1 or 2.
  • 3 to 8 valence electrons → Group = valence electrons + 10.
  • Periods are the 7 horizontal rows determined by the number of shells filled with electrons.

Short Activity

Complete all parts before checking your score.

A. Objective Quiz

1

An atom of element X has a proton number of 7. In which group and period is element X located in the Periodic Table of Elements?

2

What factor determines the period of an element in the Periodic Table of Elements?

B. Fill in the Blanks

3

The vertical columns in the Periodic Table of Elements are called _____.

4

For an element with 3 to 8 valence electrons, its group number is calculated by adding the number of valence electrons to _____.

C. Match Each Element to Its Position

Drag each element on desktop. On mobile, tap an element and then tap the matching box.

Element

Lithium, Li (proton number 3) Calcium, Ca (proton number 20) Aluminium, Al (proton number 13) Krypton, Kr (proton number 36)

Position in Periodic Table

1Group 1, Period 2
2Group 2, Period 4
3Group 13, Period 3
4Group 18, Period 4
Complete every answer before checking.
 

Keywords

Tap or hover over a term to read its meaning.

Modern Periodic Table of Elements Group Period Proton number Valence electron
The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.

The Arrangement of Elements in the Modern Periodic Table of Elements

4.2 The Arrangement in the Periodic Table of Elements
CHEMISTRY • Form 4 • Chapter 4: The Periodic Table of Elements

4.2The Arrangement in the Periodic Table of Elements

The modern Periodic Table of Elements is a systematic classification of chemical elements arranged in ascending order of their proton numbers from left to right and from top to bottom. By knowing the proton number of an atom, its electron arrangement can be determined, which directly reveals its group and period in the Periodic Table.

Learning Objectives

  • Describe briefly the modern Periodic Table of Elements.
  • Generalise the relationship between the proton number and the position of elements in the Periodic Table of Elements (groups and periods).

Determining Group and Period from Electron Arrangement

Use the number of valence electrons and the number of filled shells to locate an element in the Periodic Table.

1
Write the electron arrangement from the proton number.
2a
Count the shells filled with electrons.
Period = number of shells filled with electrons
2b
Look at the valence electrons in the outermost shell.
1 or 2 valence electrons → Group 1 or 2
3 to 8 valence electrons → Group = valence electrons + 10

Brief Explanation

Understand how groups and periods are determined.

The modern Periodic Table of Elements arranges elements in ascending order of their proton numbers from left to right and from top to bottom.

Groups

Vertical columns in the Periodic Table are called Groups. There are 18 groups. The number of valence electrons determines the group of an element.

  • 1 or 2 valence electrons → Group 1 or 2.
  • 3 to 8 valence electrons → Group = valence electrons + 10.

Periods

Horizontal rows in the Periodic Table are called Periods. There are 7 periods. The number of shells filled with electrons determines the period of an element.

  • Period = number of shells filled with electrons.
Element Proton number Electron arrangement Valence electrons Group Period
Lithium, Li 3 2.1 1 1 2
Calcium, Ca 20 2.8.8.2 2 2 4
Aluminium, Al 13 2.8.3 3 13 3
Silicon, Si 14 2.8.4 4 14 3
Nitrogen, N 7 2.5 5 15 2
Oxygen, O 8 2.6 6 16 2
Bromine, Br 35 2.8.18.7 7 17 4
Krypton, Kr 36 2.8.18.8 8 18 4

Try to Answer First

Answer mentally, then check the explanation.

1

What determines the period of an element in the Periodic Table of Elements?

Answer: The number of shells filled with electrons.
2

An element has a proton number of 14. What is its group and period?

Answer: Its electron arrangement is 2.8.4. It has 4 valence electrons, so its group is 4 + 10 = 14. It has 3 shells filled with electrons, so its period is Period 3.
3

How are elements arranged in the modern Periodic Table of Elements?

Answer: In ascending order of proton numbers from left to right and from top to bottom.

Common Mistakes

Avoid these errors when determining the position of an element.

!
Forgetting to add 10 for elements with 3 to 8 valence electrons. For example, stating that aluminium is in Group 3 instead of Group 13.
!
Confusing groups with periods, such as taking the number of shells as the group and valence electrons as the period.
!
Using the nucleon number instead of the proton number to write the electron arrangement.

Concept Misunderstandings

Compare each misconception with the correct fact.

Misconception

Elements in the modern Periodic Table are arranged according to their relative atomic mass.

Correct Fact

In the modern Periodic Table, elements are arranged in ascending order of their proton numbers.

Misconception

All elements take their group number directly from the number of valence electrons.

Correct Fact

Only elements with 1 or 2 valence electrons have a group number equal to their valence electrons; elements with 3 to 8 valence electrons must add 10 to determine their group number (Groups 13 to 18).

Summary

Key facts to remember.

  • The modern Periodic Table arranges elements in ascending order of proton numbers.
  • Groups are the 18 vertical columns determined by the number of valence electrons.
  • 1 or 2 valence electrons → Group 1 or 2.
  • 3 to 8 valence electrons → Group = valence electrons + 10.
  • Periods are the 7 horizontal rows determined by the number of shells filled with electrons.

Short Activity

Complete all parts before checking your score.

A. Objective Quiz

1

An atom of element X has a proton number of 7. In which group and period is element X located in the Periodic Table of Elements?

2

What factor determines the period of an element in the Periodic Table of Elements?

B. Fill in the Blanks

3

The vertical columns in the Periodic Table of Elements are called _____.

4

For an element with 3 to 8 valence electrons, its group number is calculated by adding the number of valence electrons to _____.

C. Match Each Element to Its Position

Drag each element on desktop. On mobile, tap an element and then tap the matching box.

Element

Lithium, Li (proton number 3) Calcium, Ca (proton number 20) Aluminium, Al (proton number 13) Krypton, Kr (proton number 36)

Position in Periodic Table

1Group 1, Period 2
2Group 2, Period 4
3Group 13, Period 3
4Group 18, Period 4
Complete every answer before checking.
 

Keywords

Tap or hover over a term to read its meaning.

Modern Periodic Table of Elements Group Period Proton number Valence electron
The views expressed in the notes here are those of the contributor and don’t necessarily represent the views of Pandai.
Chapter : Periodic Table of Elements
Topic : The Arrangement in the Periodic Table of Elements
Form 4 Chemistry
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