What is meant by periodicity of properties of elements ? Why are the properties of elements placed in the same group of the periodic table similar ?
What is meant by periodicity of properties of elements ? Why are the properties of elements placed in the same group of the periodic table similar ?
Official answer
Periodicity of properties: It is the recurrence of similar physical and chemical properties of elements after certain regular intervals when elements are arranged in the order of their increasing atomic numbers.
Similarity in Groups: The properties of elements in the same group are similar because they have the same number of valence electrons. Since chemical properties depend on the number of valence electrons and the electronic configuration of the outermost shell, elements in a group exhibit similar chemical behavior.
Marking scheme
- 1.Definition of periodicity of properties (1 mark)
- 2.Explanation of similarity based on valence electrons (1 mark)
Hint
Chemical properties are determined by the electrons in the outermost shell.
Quick oral answer
Periodicity is the repetition of properties at fixed intervals. Elements in a group are similar because they have the same number of valence electrons.
Common mistakes
- 1.Defining periodicity based on atomic mass instead of atomic number.
- 2.Attributing similarity to the total number of electrons rather than just valence electrons.
Analysis and explanation
The text mentions alkali metals like Lithium (), Sodium (), and Potassium () in Section 3.1.2. These elements are grouped together because they all have one electron in their outermost shell. This shared electronic configuration is why they all react vigorously with water (as seen in Section 3.2.2) to form alkalis and hydrogen gas.
Interesting facts
The word 'periodicity' comes from the fact that these properties repeat in 'periods', much like the phases of the moon or the days of the week.
Question details
Q6 of 41 questions
- Board
- CBSE
- Class
- Class 10
- Subject
- Science
- Year
- 2011
- Section
- Section A
- Marks
- 2
- Type
- Short Answer
- Chapter
- Metals and Non-metals
- Topic
- Periodicity of Elements
- Bloom's level
- Remembering
- Syllabus topic
- Modern Periodic Table: Periodicity and Group Characteristics
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Frequently asked questions
How many marks does this question carry in CBSE Class 10 Science 2011?
This question carries 2 marks in the CBSE Class 10 Science 2011 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Metals and Non-metals" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Periodicity of Elements" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2011 paper?
This is a Short Answer question from Section A in the CBSE Class 10 Science 2011 paper.