The positions of three elements A, B and C in the periodic table are indicated below :
Group 16 Group 17 First Period — — Second Period — A Third Period — — Fourth Period B C
(a) State whether element C would be a metal or a non-metal. Why ? (b) Which is the more active element, A or C ? Why ? (c) Which type of ion (cation or anion) will be formed by the element C ? Why ?
The positions of three elements A, B and C in the periodic table are indicated below :
| Group 16 | Group 17 | |
|---|---|---|
| First Period | — | — |
| Second Period | — | A |
| Third Period | — | — |
| Fourth Period | B | C |
(a) State whether element C would be a metal or a non-metal. Why ? (b) Which is the more active element, A or C ? Why ? (c) Which type of ion (cation or anion) will be formed by the element C ? Why ?
(a) Non-metal. Element C belongs to Group 17. Elements in Group 17 have 7 valence electrons and a high electronegativity, meaning they tend to gain electrons to complete their octet. As mentioned in Section 3.1.2, non-metals like Iodine (also in Group 17) are typically found on the right side of the periodic table.
(b) Element A is more active. In Group 17 (non-metals), reactivity decreases as we move down the group. This is because the atomic size increases, making it harder for the nucleus to attract and gain an incoming electron. Since A is in the 2nd period and C is in the 4th period, A is more reactive.
(c) Anion. Element C will form an anion. Because it has 7 valence electrons, it needs to gain one electron to achieve a stable electronic configuration (octet). Gaining an electron results in a negative charge: .
Marking Scheme
- 1Identify C as non-metal with reason (Group 17/valence electrons) (1 mark)
- 2Identify A as more active with reason (reactivity trend in non-metals) (1 mark)
- 3Identify C forms an anion with reason (electron gain for octet) (1 mark)
Hint
Group 17 elements are halogens. Recall how non-metal reactivity changes down a group.
Quick Oral Answer
Element C is a non-metal because it's in Group 17. A is more reactive than C because non-metal reactivity decreases down a group. C forms an anion by gaining one electron.
Analysis & Explanation
This question integrates the concept of non-metals from the text with periodic trends. Section 3.1.2 identifies non-metals like Iodine and Bromine (Group 17). Non-metals are characterized by their ability to form acidic oxides (Activity 3.8) and their tendency to gain electrons. In Group 17, the 'pull' for an extra electron is strongest at the top (Period 2) and weakest at the bottom, explaining why A is more active than C.
Common Mistakes
- 1Applying the metal reactivity trend (which increases down a group) to non-metals.
- 2Confusing cations (positive) with anions (negative).
Interesting Facts
Group 17 elements are called 'halogens', which means 'salt-formers', because they react with metals to form salts like .
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2011?
This question carries 3 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 Table Analysis" 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.