Physical Properties of Non-metals
अधातुओं के भौतिक गुण | Class 10 Science – Chapter 3
Physical Properties of Non-metals | अधातुओं के भौतिक गुण
1. Introduction | परिचय
Non-metals (अधातु) are elements that generally do not show the typical physical properties of metals.
अधातु वे तत्व हैं जिनमें सामान्यतः धातुओं के विशिष्ट भौतिक गुण नहीं पाए जाते हैं।
Examples / उदाहरण:
Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Phosphorus (P),
Sulphur (S), Chlorine (Cl), Bromine (Br), Iodine (I).
2. Major Physical Properties | प्रमुख भौतिक गुण
1. State of matter | पदार्थ की अवस्था
Most non-metals are gases or solids at room temperature. अधिकांश अधातु कमरे के तापमान पर गैस या ठोस अवस्था में पाए जाते हैं। Examples: Oxygen, nitrogen and chlorine → gases. Sulphur, phosphorus and carbon → solids. Bromine is a liquid non-metal at room temperature.
Most non-metals are gases or solids at room temperature. अधिकांश अधातु कमरे के तापमान पर गैस या ठोस अवस्था में पाए जाते हैं। Examples: Oxygen, nitrogen and chlorine → gases. Sulphur, phosphorus and carbon → solids. Bromine is a liquid non-metal at room temperature.
2. Generally non-lustrous | सामान्यतः चमकीले नहीं होते
Non-metals generally have a dull appearance. अधातु सामान्यतः चमकहीन होते हैं। However, there are exceptions. Iodine is a lustrous non-metal. इसलिए परीक्षा में याद रखें:
Non-metals generally have a dull appearance. अधातु सामान्यतः चमकहीन होते हैं। However, there are exceptions. Iodine is a lustrous non-metal. इसलिए परीक्षा में याद रखें:
Lustrous non-metal → Iodine (आयोडीन)
3. Brittle | भंगुर
Solid non-metals are generally brittle and break into pieces when hammered. ठोस अधातु सामान्यतः भंगुर होते हैं तथा हथौड़े से पीटने पर टूट जाते हैं। Therefore, non-metals are generally neither malleable nor ductile.
Solid non-metals are generally brittle and break into pieces when hammered. ठोस अधातु सामान्यतः भंगुर होते हैं तथा हथौड़े से पीटने पर टूट जाते हैं। Therefore, non-metals are generally neither malleable nor ductile.
4. Poor conductors of electricity | विद्युत के कुचालक
Most non-metals are poor conductors of electricity. अधिकांश अधातु विद्युत के कुचालक होते हैं। Exception: Graphite is a good conductor of electricity. अपवाद: ग्रेफाइट विद्युत का अच्छा चालक है।
Most non-metals are poor conductors of electricity. अधिकांश अधातु विद्युत के कुचालक होते हैं। Exception: Graphite is a good conductor of electricity. अपवाद: ग्रेफाइट विद्युत का अच्छा चालक है।
5. Poor conductors of heat | ऊष्मा के कुचालक
Most non-metals are poor conductors of heat. अधिकांश अधातु ऊष्मा के कुचालक होते हैं।
Most non-metals are poor conductors of heat. अधिकांश अधातु ऊष्मा के कुचालक होते हैं।
6. Low density | कम घनत्व
Many non-metals have relatively low density compared with metals. कई अधातुओं का घनत्व धातुओं की तुलना में कम होता है।
Many non-metals have relatively low density compared with metals. कई अधातुओं का घनत्व धातुओं की तुलना में कम होता है।
7. Low melting and boiling points | कम गलनांक एवं क्वथनांक
Many non-metals have relatively low melting and boiling points. कई अधातुओं के गलनांक और क्वथनांक धातुओं की तुलना में कम होते हैं। Exception: Diamond has a very high melting point because of its strong covalent structure.
Many non-metals have relatively low melting and boiling points. कई अधातुओं के गलनांक और क्वथनांक धातुओं की तुलना में कम होते हैं। Exception: Diamond has a very high melting point because of its strong covalent structure.
3. Why is Graphite a Good Conductor of Electricity?
ग्रेफाइट विद्युत का अच्छा चालक क्यों है?
ग्रेफाइट विद्युत का अच्छा चालक क्यों है?
Graphite is an allotrope of carbon.
ग्रेफाइट कार्बन का एक अपररूप (allotrope) है।
In graphite, each carbon atom is bonded to three other carbon atoms.
ग्रेफाइट में प्रत्येक कार्बन परमाणु तीन अन्य कार्बन परमाणुओं से जुड़ा होता है।
One electron remains relatively free to move through the layers.
एक इलेक्ट्रॉन अपेक्षाकृत स्वतंत्र रहता है और परतों में गति कर सकता है।
These mobile electrons carry electric current.
यही गतिशील इलेक्ट्रॉन विद्युत धारा का संचरण करते हैं।
Graphite → Delocalised electrons → Electrical conduction
4. Important Exceptions | महत्वपूर्ण अपवाद
| Property / गुण | General Nature / सामान्य प्रकृति | Exception / अपवाद |
|---|---|---|
| Lustre / चमक | Generally dull | Iodine |
| Electrical conductivity / विद्युत चालकता | Generally poor | Graphite |
| State / अवस्था | Mostly gases or solids | Bromine is liquid |
5. Important One-Liners | महत्वपूर्ण तथ्य
• Lustrous non-metal → Iodine
• Good conductor of electricity among non-metals → Graphite
• Liquid non-metal at room temperature → Bromine
• Hardest natural substance → Diamond
• Graphite and diamond → Allotropes of carbon
• Most non-metals → Poor conductors of heat and electricity
• Solid non-metals → Generally brittle
• Good conductor of electricity among non-metals → Graphite
• Liquid non-metal at room temperature → Bromine
• Hardest natural substance → Diamond
• Graphite and diamond → Allotropes of carbon
• Most non-metals → Poor conductors of heat and electricity
• Solid non-metals → Generally brittle
30 MCQs | बहुविकल्पीय प्रश्न
Q1. Which of the following is a lustrous non-metal?
निम्नलिखित में से कौन-सा चमकीला अधातु है?
निम्नलिखित में से कौन-सा चमकीला अधातु है?
A. Iodine
B. Sulphur
C. Phosphorus
D. Nitrogen
Answer: A. Iodine
Iodine is a notable exception because it has a lustrous appearance.
Iodine is a notable exception because it has a lustrous appearance.
Q2. Which non-metal is a good conductor of electricity?
कौन-सा अधातु विद्युत का अच्छा चालक है?
कौन-सा अधातु विद्युत का अच्छा चालक है?
A. Sulphur
B. Graphite
C. Phosphorus
D. Oxygen
Answer: B. Graphite
Graphite contains delocalised electrons that can carry electric current.
Graphite contains delocalised electrons that can carry electric current.
Q3. Which non-metal is liquid at room temperature?
कमरे के तापमान पर कौन-सा अधातु द्रव होता है?
कमरे के तापमान पर कौन-सा अधातु द्रव होता है?
A. Carbon
B. Sulphur
C. Bromine
D. Iodine
Answer: C. Bromine
Q4. Non-metals are generally:
अधातु सामान्यतः होते हैं:
अधातु सामान्यतः होते हैं:
A. Malleable
B. Ductile
C. Sonorous
D. Brittle
Answer: D. Brittle
Q5. Which property is generally associated with non-metals?
अधातुओं का सामान्य गुण कौन-सा है?
अधातुओं का सामान्य गुण कौन-सा है?
A. Poor electrical conductivity
B. High ductility
C. High malleability
D. Metallic lustre
Answer: A. Poor electrical conductivity
Q6. Graphite conducts electricity because it has:
ग्रेफाइट विद्युत का संचालन करता है क्योंकि इसमें होते हैं:
ग्रेफाइट विद्युत का संचालन करता है क्योंकि इसमें होते हैं:
A. Ionic bonds
B. Free/delocalised electrons
C. Metallic ions
D. Protons
Answer: B. Free/delocalised electrons
Q7. Which allotrope of carbon is a good conductor of electricity?
कार्बन का कौन-सा अपररूप विद्युत का अच्छा चालक है?
कार्बन का कौन-सा अपररूप विद्युत का अच्छा चालक है?
A. Diamond
B. Fullerene only
C. Graphite
D. Coal
Answer: C. Graphite
Q8. Most non-metals are:
अधिकांश अधातु होते हैं:
अधिकांश अधातु होते हैं:
A. Good conductors
B. Poor conductors
C. Highly malleable
D. Highly ductile
Answer: B. Poor conductors
Q9. Which of the following is a solid non-metal?
निम्न में से कौन-सा ठोस अधातु है?
निम्न में से कौन-सा ठोस अधातु है?
A. Oxygen
B. Nitrogen
C. Sulphur
D. Chlorine
Answer: C. Sulphur
Q10. Which non-metal has metallic lustre?
किस अधातु में धात्विक चमक होती है?
किस अधातु में धात्विक चमक होती है?
A. Iodine
B. Sulphur
C. Oxygen
D. Hydrogen
Answer: A. Iodine
Q11. Which of the following is generally not a property of non-metals?
निम्न में से कौन-सा सामान्यतः अधातुओं का गुण नहीं है?
निम्न में से कौन-सा सामान्यतः अधातुओं का गुण नहीं है?
A. Brittleness
B. Poor conductivity
C. Ductility
D. Dull appearance
Answer: C. Ductility
Q12. A non-metal that exists as a liquid at room temperature is:
कमरे के तापमान पर द्रव अवस्था में पाया जाने वाला अधातु है:
कमरे के तापमान पर द्रव अवस्था में पाया जाने वाला अधातु है:
A. Bromine
B. Carbon
C. Sulphur
D. Phosphorus
Answer: A. Bromine
Q13. Which substance is the hardest natural form of carbon?
कार्बन का सबसे कठोर प्राकृतिक रूप कौन-सा है?
कार्बन का सबसे कठोर प्राकृतिक रूप कौन-सा है?
A. Graphite
B. Diamond
C. Coal
D. Coke
Answer: B. Diamond
Q14. The non-metal generally considered a poor conductor of heat is:
निम्न में से अधातु सामान्यतः ऊष्मा का कुचालक है:
निम्न में से अधातु सामान्यतः ऊष्मा का कुचालक है:
A. Copper
B. Aluminium
C. Sulphur
D. Iron
Answer: C. Sulphur
Q15. Solid non-metals are generally:
ठोस अधातु सामान्यतः होते हैं:
ठोस अधातु सामान्यतः होते हैं:
A. Brittle
B. Ductile
C. Malleable
D. Sonorous
Answer: A. Brittle
Q16. Which property distinguishes graphite from most other non-metals?
कौन-सा गुण ग्रेफाइट को अधिकांश अन्य अधातुओं से अलग करता है?
कौन-सा गुण ग्रेफाइट को अधिकांश अन्य अधातुओं से अलग करता है?
A. It is brittle
B. It conducts electricity
C. It is a solid
D. It contains carbon
Answer: B. It conducts electricity
Q17. Which one is generally dull in appearance?
निम्न में से कौन सामान्यतः चमकहीन होता है?
निम्न में से कौन सामान्यतः चमकहीन होता है?
A. Sulphur
B. Silver
C. Copper
D. Aluminium
Answer: A. Sulphur
Q18. Which statement is correct about non-metals?
अधातुओं के बारे में कौन-सा कथन सही है?
अधातुओं के बारे में कौन-सा कथन सही है?
A. All are solids
B. All are gases
C. They generally lack metallic properties
D. All conduct electricity
Answer: C. They generally lack metallic properties
Q19. Which non-metal is shiny due to its surface appearance?
कौन-सा अधातु अपनी सतह के कारण चमकीला दिखाई देता है?
कौन-सा अधातु अपनी सतह के कारण चमकीला दिखाई देता है?
A. Iodine
B. Nitrogen
C. Oxygen
D. Sulphur
Answer: A. Iodine
Q20. The electrical conductivity of graphite is mainly due to:
ग्रेफाइट की विद्युत चालकता मुख्यतः किस कारण होती है?
ग्रेफाइट की विद्युत चालकता मुख्यतः किस कारण होती है?
A. Protons
B. Neutrons
C. Delocalised electrons
D. Nuclei
Answer: C. Delocalised electrons
Q21. Which of the following is NOT a non-metal?
निम्नलिखित में से कौन अधातु नहीं है?
निम्नलिखित में से कौन अधातु नहीं है?
A. Oxygen
B. Sulphur
C. Iron
D. Nitrogen
Answer: C. Iron
Q22. Non-metals generally have:
अधातुओं में सामान्यतः होता है:
अधातुओं में सामान्यतः होता है:
A. Metallic lustre
B. High ductility
C. Low conductivity
D. Sonority
Answer: C. Low conductivity
Q23. Which pair contains only non-metals?
किस युग्म में केवल अधातु हैं?
किस युग्म में केवल अधातु हैं?
A. Sulphur and Oxygen
B. Iron and Sulphur
C. Copper and Oxygen
D. Aluminium and Nitrogen
Answer: A. Sulphur and Oxygen
Q24. Which non-metal is important as an exception to poor electrical conductivity?
विद्युत के कुचालक होने के नियम का महत्वपूर्ण अपवाद कौन-सा अधातु है?
विद्युत के कुचालक होने के नियम का महत्वपूर्ण अपवाद कौन-सा अधातु है?
A. Graphite
B. Sulphur
C. Phosphorus
D. Chlorine
Answer: A. Graphite
Q25. Which property means that a substance can be beaten into thin sheets?
किस गुण का अर्थ है कि पदार्थ को पीटकर पतली चादरों में बदला जा सकता है?
किस गुण का अर्थ है कि पदार्थ को पीटकर पतली चादरों में बदला जा सकता है?
A. Ductility
B. Malleability
C. Brittleness
D. Sonority
Answer: B. Malleability
Non-metals generally do not show malleability.
Non-metals generally do not show malleability.
Q26. Which property means that a substance can be drawn into wires?
किस गुण का अर्थ है कि पदार्थ को तारों में खींचा जा सकता है?
किस गुण का अर्थ है कि पदार्थ को तारों में खींचा जा सकता है?
A. Brittleness
B. Lustre
C. Ductility
D. Density
Answer: C. Ductility
Q27. Which of the following is a gaseous non-metal?
निम्न में से कौन-सा गैसीय अधातु है?
निम्न में से कौन-सा गैसीय अधातु है?
A. Sulphur
B. Oxygen
C. Iodine
D. Carbon
Answer: B. Oxygen
Q28. Graphite and diamond are:
ग्रेफाइट और हीरा हैं:
ग्रेफाइट और हीरा हैं:
A. Isotopes
B. Isobars
C. Allotropes
D. Ions
Answer: C. Allotropes
Q29. Which statement about iodine is correct?
आयोडीन के बारे में कौन-सा कथन सही है?
आयोडीन के बारे में कौन-सा कथन सही है?
A. It is a metal
B. It is a lustrous non-metal
C. It is a gaseous metal
D. It is a liquid metal
Answer: B. It is a lustrous non-metal
Q30. Which statement best explains why non-metals are generally poor conductors?
कौन-सा कथन बताता है कि अधातु सामान्यतः कुचालक क्यों होते हैं?
कौन-सा कथन बताता है कि अधातु सामान्यतः कुचालक क्यों होते हैं?
A. They usually lack freely mobile charge carriers
B. They always contain metal ions
C. They are always liquids
D. They have metallic bonding
Answer: A. They usually lack freely mobile charge carriers
30 Subjective Questions with Answers | वर्णनात्मक प्रश्न एवं उत्तर
1 Mark
Q1. What are non-metals?
अधातु क्या हैं?
Q1. What are non-metals?
अधातु क्या हैं?
Answer: Non-metals are elements that generally do not possess the typical physical properties of metals.
अधातु वे तत्व हैं जिनमें सामान्यतः धातुओं के विशिष्ट भौतिक गुण नहीं होते हैं।
अधातु वे तत्व हैं जिनमें सामान्यतः धातुओं के विशिष्ट भौतिक गुण नहीं होते हैं।
1 Mark
Q2. Name a lustrous non-metal.
एक चमकीले अधातु का नाम लिखिए।
Q2. Name a lustrous non-metal.
एक चमकीले अधातु का नाम लिखिए।
Answer: Iodine (आयोडीन).
1 Mark
Q3. Name a non-metal that conducts electricity.
ऐसे अधातु का नाम लिखिए जो विद्युत का संचालन करता है।
Q3. Name a non-metal that conducts electricity.
ऐसे अधातु का नाम लिखिए जो विद्युत का संचालन करता है।
Answer: Graphite (ग्रेफाइट).
1 Mark
Q4. Name the liquid non-metal at room temperature.
कमरे के तापमान पर द्रव अधातु का नाम लिखिए।
Q4. Name the liquid non-metal at room temperature.
कमरे के तापमान पर द्रव अधातु का नाम लिखिए।
Answer: Bromine (ब्रोमीन).
1 Mark
Q5. What is the physical state of oxygen at room temperature?
कमरे के तापमान पर ऑक्सीजन की भौतिक अवस्था क्या है?
Q5. What is the physical state of oxygen at room temperature?
कमरे के तापमान पर ऑक्सीजन की भौतिक अवस्था क्या है?
Answer: Gaseous state / गैसीय अवस्था.
2 Marks
Q6. Write any two physical properties of non-metals.
अधातुओं के कोई दो भौतिक गुण लिखिए।
Q6. Write any two physical properties of non-metals.
अधातुओं के कोई दो भौतिक गुण लिखिए।
Answer:
1. They are generally poor conductors of electricity.
2. Solid non-metals are generally brittle.
1. They are generally poor conductors of electricity.
2. Solid non-metals are generally brittle.
2 Marks
Q7. Why are non-metals generally poor conductors of electricity?
अधातु सामान्यतः विद्युत के कुचालक क्यों होते हैं?
Q7. Why are non-metals generally poor conductors of electricity?
अधातु सामान्यतः विद्युत के कुचालक क्यों होते हैं?
Answer: Non-metals generally do not have freely mobile electrons available for carrying electric current. Hence, they are generally poor conductors.
2 Marks
Q8. Why is iodine considered an exception among non-metals?
आयोडीन को अधातुओं में अपवाद क्यों माना जाता है?
Q8. Why is iodine considered an exception among non-metals?
आयोडीन को अधातुओं में अपवाद क्यों माना जाता है?
Answer: Most non-metals are dull, but iodine has a shiny or lustrous appearance. Hence iodine is an exception.
2 Marks
Q9. What is meant by brittleness?
भंगुरता से क्या तात्पर्य है?
Q9. What is meant by brittleness?
भंगुरता से क्या तात्पर्य है?
Answer: The tendency of a solid substance to break into pieces when hammered or subjected to force is called brittleness.
2 Marks
Q10. Give two examples of gaseous non-metals.
दो गैसीय अधातुओं के उदाहरण दीजिए।
Q10. Give two examples of gaseous non-metals.
दो गैसीय अधातुओं के उदाहरण दीजिए।
Answer: Oxygen and Nitrogen.
3 Marks
Q11. Explain three physical properties of non-metals.
अधातुओं के तीन भौतिक गुण समझाइए।
Q11. Explain three physical properties of non-metals.
अधातुओं के तीन भौतिक गुण समझाइए।
Answer:
1. They are generally poor conductors of heat and electricity.
2. Solid non-metals are generally brittle.
3. They generally do not have metallic lustre.
1. They are generally poor conductors of heat and electricity.
2. Solid non-metals are generally brittle.
3. They generally do not have metallic lustre.
3 Marks
Q12. Explain why graphite conducts electricity.
ग्रेफाइट विद्युत का संचालन क्यों करता है?
Q12. Explain why graphite conducts electricity.
ग्रेफाइट विद्युत का संचालन क्यों करता है?
Answer:
In graphite, each carbon atom is bonded to three other carbon atoms. One electron remains delocalised and can move through the structure. These mobile electrons carry electric current.
In graphite, each carbon atom is bonded to three other carbon atoms. One electron remains delocalised and can move through the structure. These mobile electrons carry electric current.
3 Marks
Q13. Give three examples showing exceptions in the physical properties of non-metals.
अधातुओं के भौतिक गुणों में तीन अपवाद उदाहरण सहित लिखिए।
Q13. Give three examples showing exceptions in the physical properties of non-metals.
अधातुओं के भौतिक गुणों में तीन अपवाद उदाहरण सहित लिखिए।
Answer:
1. Iodine is lustrous.
2. Graphite conducts electricity.
3. Bromine is liquid at room temperature.
1. Iodine is lustrous.
2. Graphite conducts electricity.
3. Bromine is liquid at room temperature.
3 Marks
Q14. Differentiate between malleability and brittleness.
आघातवर्धनीयता और भंगुरता में अंतर लिखिए।
Q14. Differentiate between malleability and brittleness.
आघातवर्धनीयता और भंगुरता में अंतर लिखिए।
Answer:
Malleability: Ability to be beaten into thin sheets.
Brittleness: Tendency to break into pieces when hammered.
Non-metals are generally brittle and not malleable.
Malleability: Ability to be beaten into thin sheets.
Brittleness: Tendency to break into pieces when hammered.
Non-metals are generally brittle and not malleable.
3 Marks
Q15. State the physical states of non-metals with examples.
अधातुओं की भौतिक अवस्थाएँ उदाहरण सहित बताइए।
Q15. State the physical states of non-metals with examples.
अधातुओं की भौतिक अवस्थाएँ उदाहरण सहित बताइए।
Answer:
• Gases: Oxygen, Nitrogen, Chlorine
• Solids: Sulphur, Carbon, Phosphorus
• Liquid: Bromine
• Gases: Oxygen, Nitrogen, Chlorine
• Solids: Sulphur, Carbon, Phosphorus
• Liquid: Bromine
4 Marks
Q16. Describe four physical properties of non-metals.
अधातुओं के चार भौतिक गुणों का वर्णन कीजिए।
Q16. Describe four physical properties of non-metals.
अधातुओं के चार भौतिक गुणों का वर्णन कीजिए।
Answer:
1. Most non-metals are poor conductors of heat and electricity.
2. Solid non-metals are generally brittle.
3. Most non-metals are dull in appearance.
4. Many non-metals have relatively low melting and boiling points.
1. Most non-metals are poor conductors of heat and electricity.
2. Solid non-metals are generally brittle.
3. Most non-metals are dull in appearance.
4. Many non-metals have relatively low melting and boiling points.
4 Marks
Q17. Explain the importance of graphite as an exception among non-metals.
अधातुओं में ग्रेफाइट के अपवाद होने का महत्व समझाइए।
Q17. Explain the importance of graphite as an exception among non-metals.
अधातुओं में ग्रेफाइट के अपवाद होने का महत्व समझाइए।
Answer:
Graphite is a non-metal and an allotrope of carbon. Unlike most non-metals, it conducts electricity. Each carbon atom forms three bonds, leaving one electron relatively delocalised. These electrons can move and conduct electricity.
Graphite is a non-metal and an allotrope of carbon. Unlike most non-metals, it conducts electricity. Each carbon atom forms three bonds, leaving one electron relatively delocalised. These electrons can move and conduct electricity.
4 Marks
Q18. Compare metals and non-metals on the basis of four physical properties.
चार भौतिक गुणों के आधार पर धातुओं और अधातुओं की तुलना कीजिए।
Q18. Compare metals and non-metals on the basis of four physical properties.
चार भौतिक गुणों के आधार पर धातुओं और अधातुओं की तुलना कीजिए।
Answer:
Metals are generally lustrous, malleable, ductile and good conductors.
Non-metals are generally dull, brittle, non-ductile and poor conductors.
Metals are generally lustrous, malleable, ductile and good conductors.
Non-metals are generally dull, brittle, non-ductile and poor conductors.
4 Marks
Q19. Why can non-metals generally not be drawn into wires?
अधातुओं को सामान्यतः तारों में क्यों नहीं खींचा जा सकता?
Q19. Why can non-metals generally not be drawn into wires?
अधातुओं को सामान्यतः तारों में क्यों नहीं खींचा जा सकता?
Answer: Non-metals are generally brittle and do not possess ductility. Therefore, they break rather than being drawn into wires.
4 Marks
Q20. Explain why solid non-metals are generally brittle.
ठोस अधातु सामान्यतः भंगुर क्यों होते हैं?
Q20. Explain why solid non-metals are generally brittle.
ठोस अधातु सामान्यतः भंगुर क्यों होते हैं?
Answer: The particles in solid non-metals are held in structures that do not allow the layers to slide easily under force. Therefore, when hammered, they tend to break rather than change shape.
5 Marks
Q21. Describe the physical properties of non-metals in detail.
अधातुओं के भौतिक गुणों का विस्तार से वर्णन कीजिए।
Q21. Describe the physical properties of non-metals in detail.
अधातुओं के भौतिक गुणों का विस्तार से वर्णन कीजिए।
Answer:
1. Most non-metals are poor conductors of heat and electricity.
2. Solid non-metals are generally brittle.
3. They generally have a dull appearance.
4. They are neither malleable nor ductile.
5. Many have comparatively low melting and boiling points.
Important exceptions include iodine, graphite and bromine.
1. Most non-metals are poor conductors of heat and electricity.
2. Solid non-metals are generally brittle.
3. They generally have a dull appearance.
4. They are neither malleable nor ductile.
5. Many have comparatively low melting and boiling points.
Important exceptions include iodine, graphite and bromine.
5 Marks
Q22. Explain the exceptions in the physical properties of non-metals.
अधातुओं के भौतिक गुणों के अपवादों को समझाइए।
Q22. Explain the exceptions in the physical properties of non-metals.
अधातुओं के भौतिक गुणों के अपवादों को समझाइए।
Answer:
• Iodine is a lustrous non-metal.
• Graphite is a good conductor of electricity.
• Bromine is a liquid non-metal at room temperature.
These examples show that physical properties cannot always be used as absolute rules.
• Iodine is a lustrous non-metal.
• Graphite is a good conductor of electricity.
• Bromine is a liquid non-metal at room temperature.
These examples show that physical properties cannot always be used as absolute rules.
5 Marks
Q23. Explain the structure of graphite responsible for its electrical conductivity.
ग्रेफाइट की विद्युत चालकता के लिए उत्तरदायी संरचना समझाइए।
Q23. Explain the structure of graphite responsible for its electrical conductivity.
ग्रेफाइट की विद्युत चालकता के लिए उत्तरदायी संरचना समझाइए।
Answer:
Each carbon atom in graphite is bonded to three neighbouring carbon atoms. The fourth valence electron is relatively delocalised. These electrons can move through the layers and carry electric current. Therefore, graphite conducts electricity.
Each carbon atom in graphite is bonded to three neighbouring carbon atoms. The fourth valence electron is relatively delocalised. These electrons can move through the layers and carry electric current. Therefore, graphite conducts electricity.
5 Marks
Q24. Why are non-metals generally considered poor conductors of heat and electricity?
अधातुओं को सामान्यतः ऊष्मा और विद्युत का कुचालक क्यों माना जाता है?
Q24. Why are non-metals generally considered poor conductors of heat and electricity?
अधातुओं को सामान्यतः ऊष्मा और विद्युत का कुचालक क्यों माना जाता है?
Answer:
Non-metals generally do not possess a large number of freely mobile electrons. Therefore, transfer of electrical charge and thermal energy is generally less efficient. Hence they are poor conductors.
Non-metals generally do not possess a large number of freely mobile electrons. Therefore, transfer of electrical charge and thermal energy is generally less efficient. Hence they are poor conductors.
5 Marks
Q25. Explain the terms lustre, malleability, ductility and brittleness.
चमक, आघातवर्धनीयता, तन्यता और भंगुरता को समझाइए।
Q25. Explain the terms lustre, malleability, ductility and brittleness.
चमक, आघातवर्धनीयता, तन्यता और भंगुरता को समझाइए।
Answer:
Lustre: Shiny appearance of a surface.
Malleability: Ability to be beaten into sheets.
Ductility: Ability to be drawn into wires.
Brittleness: Tendency to break under force.
Lustre: Shiny appearance of a surface.
Malleability: Ability to be beaten into sheets.
Ductility: Ability to be drawn into wires.
Brittleness: Tendency to break under force.
6 Marks
Q26. Give a detailed comparison between metals and non-metals based on physical properties.
धातुओं और अधातुओं के भौतिक गुणों के आधार पर विस्तृत तुलना कीजिए।
Q26. Give a detailed comparison between metals and non-metals based on physical properties.
धातुओं और अधातुओं के भौतिक गुणों के आधार पर विस्तृत तुलना कीजिए।
Answer:
Metals:
• Generally lustrous
• Generally malleable
• Generally ductile
• Generally good conductors
• Generally sonorous
Non-metals:
• Generally dull
• Generally brittle
• Generally non-ductile
• Generally poor conductors
• Generally non-sonorous
Metals:
• Generally lustrous
• Generally malleable
• Generally ductile
• Generally good conductors
• Generally sonorous
Non-metals:
• Generally dull
• Generally brittle
• Generally non-ductile
• Generally poor conductors
• Generally non-sonorous
6 Marks
Q27. Explain the physical properties of non-metals and mention important exceptions.
अधातुओं के भौतिक गुणों को समझाते हुए महत्वपूर्ण अपवाद लिखिए।
Q27. Explain the physical properties of non-metals and mention important exceptions.
अधातुओं के भौतिक गुणों को समझाते हुए महत्वपूर्ण अपवाद लिखिए।
Answer:
Non-metals are generally dull, brittle, non-malleable, non-ductile and poor conductors of heat and electricity. Many have low melting and boiling points.
Exceptions:
Iodine is lustrous, graphite conducts electricity and bromine is liquid at room temperature.
Non-metals are generally dull, brittle, non-malleable, non-ductile and poor conductors of heat and electricity. Many have low melting and boiling points.
Exceptions:
Iodine is lustrous, graphite conducts electricity and bromine is liquid at room temperature.
6 Marks
Q28. A student says, "All non-metals are poor conductors of electricity." Is the statement completely correct? Explain.
एक विद्यार्थी कहता है, "सभी अधातु विद्युत के कुचालक होते हैं।" क्या यह कथन पूर्णतः सही है? समझाइए।
Q28. A student says, "All non-metals are poor conductors of electricity." Is the statement completely correct? Explain.
एक विद्यार्थी कहता है, "सभी अधातु विद्युत के कुचालक होते हैं।" क्या यह कथन पूर्णतः सही है? समझाइए।
Answer:
No. The statement is not completely correct. Most non-metals are poor conductors, but graphite is a good conductor of electricity because it contains relatively mobile delocalised electrons.
No. The statement is not completely correct. Most non-metals are poor conductors, but graphite is a good conductor of electricity because it contains relatively mobile delocalised electrons.
6 Marks
Q29. Why are physical properties alone not sufficient to identify an element as a metal or non-metal?
किसी तत्व को धातु या अधातु पहचानने के लिए केवल भौतिक गुण पर्याप्त क्यों नहीं हैं?
Q29. Why are physical properties alone not sufficient to identify an element as a metal or non-metal?
किसी तत्व को धातु या अधातु पहचानने के लिए केवल भौतिक गुण पर्याप्त क्यों नहीं हैं?
Answer:
Although metals and non-metals show general differences, several exceptions exist. Iodine is lustrous, graphite conducts electricity and bromine is liquid. Therefore, chemical properties along with physical properties are important for proper classification.
Although metals and non-metals show general differences, several exceptions exist. Iodine is lustrous, graphite conducts electricity and bromine is liquid. Therefore, chemical properties along with physical properties are important for proper classification.
6 Marks
Q30. Prepare a complete note on "Physical Properties of Non-metals".
"अधातुओं के भौतिक गुण" पर विस्तृत टिप्पणी लिखिए।
Q30. Prepare a complete note on "Physical Properties of Non-metals".
"अधातुओं के भौतिक गुण" पर विस्तृत टिप्पणी लिखिए।
Answer:
Non-metals generally have the following physical properties:
1. They are generally dull in appearance.
2. Solid non-metals are generally brittle.
3. They are generally neither malleable nor ductile.
4. They are poor conductors of heat and electricity.
5. Many have relatively low melting and boiling points.
6. They occur in solid, liquid and gaseous states.
Important exceptions are iodine, which is lustrous; graphite, which conducts electricity; and bromine, which is liquid at room temperature.
Non-metals generally have the following physical properties:
1. They are generally dull in appearance.
2. Solid non-metals are generally brittle.
3. They are generally neither malleable nor ductile.
4. They are poor conductors of heat and electricity.
5. Many have relatively low melting and boiling points.
6. They occur in solid, liquid and gaseous states.
Important exceptions are iodine, which is lustrous; graphite, which conducts electricity; and bromine, which is liquid at room temperature.
Exam Revision Points | परीक्षा के लिए त्वरित पुनरावृत्ति
★ Most Important Facts:
1. Lustrous non-metal → Iodine
2. Good conductor among non-metals → Graphite
3. Liquid non-metal → Bromine
4. Hardest natural substance → Diamond
5. Graphite is an allotrope of → Carbon
6. Solid non-metals are generally → Brittle
7. Non-metals are generally → Poor conductors
8. Graphite conducts because of → Delocalised electrons
1. Lustrous non-metal → Iodine
2. Good conductor among non-metals → Graphite
3. Liquid non-metal → Bromine
4. Hardest natural substance → Diamond
5. Graphite is an allotrope of → Carbon
6. Solid non-metals are generally → Brittle
7. Non-metals are generally → Poor conductors
8. Graphite conducts because of → Delocalised electrons
