In the periodic table, how does the tendency of atoms to lose electrons change on going from (i) left to right across a period ? (ii) top to bottom in a group ?
In the periodic table, how does the tendency of atoms to lose electrons change on going from (i) left to right across a period ? (ii) top to bottom in a group ?
Official answer
The tendency of atoms to lose electrons changes as follows:
(i) Left to right across a period: The tendency to lose electrons decreases. This is because the effective nuclear charge increases as the atomic number increases, pulling the valence electrons closer to the nucleus and making them harder to remove.
(ii) Top to bottom in a group: The tendency to lose electrons increases. As we move down a group, new shells are added, increasing the atomic size. The distance between the nucleus and the outermost electrons increases, weakening the nuclear attraction and making it easier for the atom to lose electrons.
Marking scheme
- 1.Correct trend and reason for 'Left to right across a period' (1 mark)
- 2.Correct trend and reason for 'Top to bottom in a group' (1 mark)
Hint
Think about how the distance between the nucleus and the outermost electron changes as you move in the periodic table.
Quick oral answer
The tendency to lose electrons is known as metallic character or electropositivity. It decreases across a period and increases down a group.
Common mistakes
- 1.Stating that the tendency to lose electrons increases across a period because there are more electrons.
- 2.Confusing the trend of losing electrons with the trend of gaining electrons.
Analysis and explanation
In the context of the provided text, metals like Sodium () and Potassium () (Section 3.1.2) are highly electropositive, meaning they lose electrons easily. Across a period, elements transition from metals (electron losers) to non-metals (electron gainers), hence the tendency to lose electrons decreases. Down a group, the 'metallic character' increases because the valence electrons are further from the nucleus and can be lost more readily.
Interesting facts
Alkali metals like Cesium () have such a high tendency to lose electrons that they can even lose them when exposed to light (photoelectric effect).
Question details
Q5 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
- Periodic Trends in Properties
- Bloom's level
- Understanding
- Syllabus topic
- Modern Periodic Table: Trends in properties (Metallic and Non-metallic character)
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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 "Periodic Trends in Properties" 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.