WBBSE Solutions For Class 8 School Science Chapter 2 Element Compound And Chemical Reaction Structure Of Matter Review Questions

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Chapter 2 Element, Compound, and Chemical Reaction Structure Of Matter MCQs

 

Question 1. The chemical property of an element depends on

  1. Number of electrons
  2. Number of protons
  3. Number of neutron
  4. Number of nucleons

Answer: 2. Number of protons

Question 2. The heaviest sub-atomic particle within an atom is

  1. Neutron
  2. Proton
  3. Electron
  4. Nucleon

Answer: 1. Neutron

Question 3. The mass of a proton

  1. Is lower than that of neutron
  2. Is lower than that of an electron
  3. Higher than that of neutron
  4. Is same as the mass of the atom

Answer: 1. Is lower than that of neutron

Question 4. The stability of the nucleus is due to

  1. Electrostatic force
  2. Nuclear force
  3. Gravitational force
  4. Magnetic force

Answer: 2. Nuclear force

Question 5. The atomic number of an element x is

  1. 10
  2. 11
  3. 15
  4. 16

Answer: 1. 10

Question 6. The formula of a compound is x³y. The valency of the element y is

  1. 1
  2. 4
  3. 2
  4. 3

Answer: 2. 4

Read And Learn More WBBSE Solutions For Class 8 School Science Review Questions

Question 7. The number of electrons in

  1. 6
  2. 14
  3. 8
  4. 20

Answer: 1. 6

Question 8. 14 C and 44 n are

  1. Isotope
  2. Isotone
  3. Isobar
  4. Iso electronic species

Answer: 3. Isobar

Question 9. One isotope of hydrogen (11 h) is

  1. Deuterium
  2. Helium
  3. H+
  4. None of these

Answer: 1. Deuterium

Question 10. The element which has no natural isotope is

  1. F
  2. H
  3. O
  4. C

Answer: 1. F

Question 11. Ionic compounds are usually

  1. Solid
  2. Liquid
  3. Gaseous
  4. Plasma

Answer: 1. Solid

Question 12. The particles which conduct electricity within molten sodium chloride are

  1. Electrons
  2. Na+ and Cl– ions
  3. Protons.
  4. Valence electrons

Answer: 2.

  1. Na+ and Cl– ions

Question 13. The formula of magnesium chloride is

  1. Mgcl
  2. Mgcl2
  3. Mg2cl
  4. Mg2cl2

Answer: 2. Mgcl2

Question 14. The number of isotopes of hydrogen is

  1. 2
  2. 3
  3. 4
  4. 1

Answer: 2. 2

Question 15. The number of electrons in an ion y+ is 10. The atomic number of the element y is

  1. 10
  2. 8
  3. 9
  4. 11

Answer: 1. 10

Question 16. Covalent compounds will be formed between which pair?

  1. A metal and a non-metal
  2. Two non-metals
  3. Two metals
  4. None of these

Answer: 2. Two non-metals

Question 17. The valency of the central atom in methane is

  1. 4
  2. 1
  3. 2
  4. 3

Answer: 1. 4

Question 18. Which of the following is an ionic compound: pcl3, mgcl2, ccl4

  1. MgCl2
  2. PCl3
  3. CCl4
  4. None

Answer: 1. Mgcl2

Question 19. which of the following is a covalent compound: Cao, H2O, KCl

  1. H20
  2. KCl
  3. Cao
  4. None

Answer: 1. H2O

Question 20. The state of matter which does not have a definite shape but has a definite volume is

  1. Liquid
  2. Solid
  3. Gas
  4. Vapor

Answer: 1. Liquid

Question 21. yxa and yx+1a are two isotopes of an element

A. The difference between the number of neutrons in the isotopes is

  1. 1 – 2Y
  2. L-x
  3. 2X-y
  4. 1

Answer: 4. 1

Question 22. The smallest particle of a substance (element or compound) which has the property of that substance and can exist independently is called

  1. An atom
  2. A molecule
  3. An ion
  4. A fundamental particle

Answer: 2. A molecule

 

Chapter 2 Element Compound, and Chemical Reaction Structure Of Matter Fill in the Blanks

 

Question 1. Most of the space occupied by an atom is practical _________.
Answer: Empty

Question 2. Nearly all mass of the atom is concentrated in a very small, dense, centrally located portion within it, called _________.
Answer: Nucleus

Question 3. The nucleus contains the entire _________ charge of an atom.
Answer: Positive

Question 4. A hydrogen atom is unique in the sense that it is the only atom that has no;_________ in its nucleus.
Answer: Neutron

Question 5. The total number of protons in the nucleus of an atom is called the _________ number of the atom.
Answer: Atomic

Question 6. The total number of protons and neutrons in the nucleus of an atom is called its _________ number
Answer: Mass

Question 7. The mass number of 126C is _________
Answer: 12

Question 8. The atomic number of 42 C is _________.
Answer: 6

Question 9. So two isotopes have the same number of but different numbers of _________.
Answer: protons, neutrons

Question 10. Atoms of different elements that have the same _________ number are called isobars.
Answer: Mass

Question 11. Atoms of different elements having the same number of _________ in the nucleus are called isotones.
Answer: Neutrons

Question 12. The lightest particle within an atom is _________
Answer: Electron

Question 13. The heaviest particle within the nucleus is _________
Answer: Proton, neutrons

Question 14. The number of neutrons in 147 N is _________
Answer: 7

Question 15. Chadwick discovered _________.
Answer: Electron

Question 16. Carbon tetrachloride is a _________compound.
Answer: Neutron

Question 17. Sodium chloride is _________compound.
Answer: Ionic

Question 18. The valency of iron may be and _________
Answer: 2,3

Question 19. Iron is an element with_________valency.
Answer: Variable

Question 20. The central atom in NCI3 is _________.
Answer: N

Question 21. The charge on sodium ion is _________.
Answer: +1

Question 22. K-shell can accommodate a maximum of _________ electrons.
Answer: 2

Question 23. Total number of covalent bonds in water is_________
Answer: 2

 

Chapter 2 Element Compound And Chemical Reaction Structure Of Matter Identify As ‘True Or False

Question 1. Proton is a positively charged particle.
Answer: True

Question2. A neutron is an uncharged particle.
Answer: True

Question 3. Protons and neutrons exist within the nucleus of an atom.
Answer: True

Question 4. Electron revolves around the nucleus.
Answer: True

Question 5. Most of the region within an atom is occupied by the nucleus.
Answer: False

Question 6. Nuclear force exists between protons and electrons.
Answer: False

Question 7. Atoms of the same element having different numbers of neutrons are called isotopes.
Answer: True

Question 8. Among the sub-atomic particles, the neutron is the heaviest.
Answer: True

Question 9. The valency of iron in ferrous compounds is two.
Answer: True

Question 10. The molecules in gas or in liquid state cannot move from one place to other.
Answer: False

Question 11. Anions or cations are always monoatomic.
Answer: False

Question 12. An atom of gold is lighter than an atom of iron.
Answer: False

Question 13. Plasma is a most abundant state of matter in the universe.
Answer: True

Question 14. Plasma is present within the stars including the sun.
Answer: True

Question 15. Crystalline solids have definite shapes.
Answer: True

Question 16. In an atom, the number of protons is the same as the number of electrons.
Answer: True

Question 17. H20 is a covalent compound.
Answer: True

Question 18. MgCI2 is an ionic compound.
Answer: True

Question 19. In a molecule of a covalent compound, the atom of an element having the lowest valency is called a central atom.
Answer: False

Question 20. The mass of the neutron and proton is approximately the same.
Answer: True

Question 21. A covalent bond is basically a pair of electrons shared equally by two atoms.
Answer: True

Question 22. It is difficult to produce ions from inert gas atoms.
Answer: True

Question 23. Magnesium ion is represented by Mg+
Answer: False

Question 24. In the case of ionic compounds, molecules do not exist.
Answer: True

Question 25. The formula of the sulfate ion is SO2+4.
Answer: False

Question 26. The valency of the central atom in carbon tetrachloride is 4.
Answer: True

 

Chapter 2 Element Compound And Chemical Reaction Structure Of Matter Match The Columns

 

Column – A Column-B
A.  Electron 1. heaviest particle within the nucleus
B. Neutron 2. negatively charged
C. Proton 3. almost the entire mass of an atom
D. Nucleus 4. 1836 times heavier than an electron

 

Answer: A-2,B-1,C-4,4-3

Column – A Column-B
A. NCl3 1. no molecule exists in a solid state
B. H2O 2. no natural isotopes
C. NaCl 3. central atom is N
D. F 4. two covalent bonds

 

Answer: A-3,B-2,C-1,4-4

 

Column – A Column-B
A. isotope 1. 146 and 147N
B. Isotone 2. 4020Ca and  3717Cl
C. Isobar 3. 136C and 146C
D. Isoelectroni 4. O2– and Na+

 

Answer: A-3,B-4,C-1,4-2

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