Chapter 2 - "Atoms, Elements and Compound" - Short Questions

"Atoms, Elements and Compound" - Short Questions:-

1. What is an element?
Answer: A pure substance made of only one type of atom.

2. Can an element be broken down by chemical methods?
Answer: No.

3. Give one example of an element.
Answer: Iron or oxygen.

4. What is a compound?
Answer: A substance formed when two or more elements are chemically combined.

5. Do compounds have fixed proportions?
Answer: Yes.

6. Give one example of a compound.
Answer: Water.

7. How can a compound be separated?
Answer: By chemical reactions.

8. What is a mixture?
Answer: Two or more substances not chemically combined.

9. Do substances in a mixture keep their own properties?
Answer: Yes.

10. mixtures have variable composition?
Answer: Yes.

11. Give one example of a mixture.
Answer: Air.

12. Name one method to separate a mixture.
Answer: Filtration.

13. Is seawater a compound or a mixture?
Answer: A mixture.

14. Is carbon dioxide an element or a compound?
Answer: A compound.

15. Is air chemically bonded?
Answer: No.

16. What is an atom?
Answer: The smallest particle of an element that takes part in reactions.

17. Where is most of the mass of an atom found?
Answer: In the nucleus.

18. What particles are found in the nucleus?
Answer: Protons and neutrons.

19. What charge does a proton have?
Answer: +1.

20. What charge does a neutron have?
Answer: 0.

21. What charge does an electron have?
Answer: −1.

22. Which particle is lightest?
Answer: Electron.

23. Where are electrons found?
Answer: In shells around the nucleus.

24. Why is the nucleus positively charged?
Answer: Because it contains protons.

25. Why are atoms mostly empty space?
Answer: The nucleus is very small compared to the atom.

26. Which particles determine the element?
Answer: Protons.

27. What is the proton number?
Answer: The number of protons in the nucleus.

28. What is another name for proton number?
Answer: Atomic number.

29. Do chemical reactions change the nucleus?
Answer: No.

30.Do nuclear reactions change elements?
Answer: Yes.

31. What is the mass number?
Answer: Total number of protons and neutrons.

32. How is mass number calculated?
Answer: Protons + neutrons.

33. What is the mass number of oxygen with 8 protons and 8 neutrons?
Answer: 16.

34. How many neutrons are in sodium-23?
Answer: 12.

35. What are isotopes?
Answer: Atoms of the same element with different numbers of neutrons.

36. Do isotopes have the same proton number?
Answer: Yes.

37. Do isotopes have the same chemical properties?
Answer: Yes.

38. Why do isotopes have the same chemistry?
Answer: Same electronic configuration.

39. Do isotopes have different masses?
Answer: Yes.

40. Name two isotopes of chlorine.
Answer: Chlorine-35 and chlorine-37.

41. Which isotope of chlorine is heavier?
Answer: Chlorine-37.

42. What changes between isotopes?
Answer: Number of neutrons.

43. Can isotopes be separated chemically?
Answer: No.

44. What property differs between isotopes?
Answer: Physical properties.

45. Where is the mass number written in atomic notation?
Answer: Top left.

46. Where is the proton number written?
Answer: Bottom left.

47. How many neutrons in ¹²₆C?
Answer: 6.

48. What does the symbol C represent?
Answer: Carbon.

49. Does proton number ever change in reactions?
Answer: No.

50. Does mass number change in chemical reactions?
Answer: No.

51. What is electronic configuration?
Answer: Arrangement of electrons in shells.

52. How many electrons fit in the first shell?
Answer: 2.

53. How many electrons fit in the second shell?
Answer: 8.

54. How many electrons fit in the third shell (up to element 20)?
Answer: 8.

55. What is the configuration of oxygen?
Answer: 2,6.

56. What is the configuration of neon?
Answer: 2,8.

57. Why are noble gases unreactive?
Answer: Full outer shell.

58. What is the configuration of sodium?
Answer: 2,8,1.

59. What is the configuration of magnesium?
Answer: 2,8,2.

60. What is the configuration of aluminium?
Answer: 2,8,3.

61. What happens to electrons during ion formation?
Answer: They are lost or gained.

62. Do protons change during ion formation?
Answer: No.

63. What is a stable electronic arrangement?
Answer: Full outer shell.

64. Why do atoms react?
Answer: To gain a stable configuration.

65. Which electrons are involved in reactions?
Answer: Outer shell electrons.

66. What is an ion?
Answer: A charged atom or group of atoms.

67. How is a positive ion formed?
Answer: By losing electrons.

68. What is a positive ion called?
Answer: A cation.

69. How is a negative ion formed?
Answer: By gaining electrons.

70. What is a negative ion called?
Answer: An anion.

71. What ion does sodium form?
Answer: Na⁺.

72. What ion does magnesium form?
Answer: Mg²⁺.

73. What ion does chlorine form?
Answer: Cl⁻.

74. What ion does oxygen form?
Answer: O²⁻.

75. What is an ionic bond?
Answer: Electrostatic attraction between opposite ions.

76. Does ionic bonding involve sharing electrons?
Answer: No.

77. Which elements usually form ionic bonds?
Answer: Metals and non-metals.

78. What structure do ionic compounds form?
Answer: Giant ionic lattice.

79. Why do ionic compounds have high melting points?
Answer: Strong attractions between ions.

80. When do ionic compounds conduct electricity?
Answer: When molten or dissolved.

81. is a covalent bond?
Answer: A shared pair of electrons.

82. Which elements form covalent bonds?
Answer: Non-metals.

83. How many bonds does hydrogen form?
Answer: One.

84. How many bonds does oxygen form?
Answer: Two.

85. How many bonds does nitrogen form?
Answer: Three.

86. How many bonds does carbon form?
Answer: Four.

87. Why do simple molecules have low melting points?
Answer: Weak intermolecular forces.

88. Do simple molecules conduct electricity?
Answer: No.

89. Why does graphite conduct electricity?
Answer: Delocalised electrons.

90. Why is graphite soft?
Answer: Weak forces between layers.

91. Why is diamond hard?
Answer: Strong covalent bonds in a 3D network.

92. Why does diamond not conduct electricity?
Answer: No free electrons.

93. What type of structure does SiO₂ have?
Answer: Giant covalent structure.

94. What is metallic bonding?
Answer: Attraction between metal ions and delocalised electrons.

95. Why do metals conduct electricity?
Answer: Mobile delocalised electrons.

96. Why are metals malleable?
Answer: Layers slide while bonding remains.

97. Why are metals ductile?
Answer: Non-directional bonding.

98. What structure do metals have?
Answer: Giant metallic lattice.

99. Which bonding has delocalised electrons?
Answer: Metallic bonding.

100. What determines the properties of substances?
Answer: Structure and bonding.

Thank You!

Sana Shariq

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