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

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Chapter 2 Element, Compound, And Chemical Reaction Structure Of Matter VSAQs

 

Question 1. An element forms a chloride XCI5. What is the valency of X?
Answer:

Given:

An element forms a chloride XCI5.

The valency of X is 5

Question 2. Who first suggested the existence of molecules?
Answer

Avogadro first suggested the existence of molecules.

Question 3. What do the symbols convey 1. H2 2. H+
Answer:

  1. H2: a molecule of hydrogen
  2. H+: a hydrogen cation

Question 4. What do you mean by mass number?
Answer:

Mass Number:

Mass number is the sum of the number of protons and neutrons present in the nucleus of an atom.

Question 5. Who confirmed the existence of neutrons experimentally?
Answer:

Chadwick (in 1932) confirmed the existence of neutrons experimentally.

Question 6. The nucleus of which element does not have a neutron?
Answer:

Nucleus of a Hydrogen atom does not have a neutron.

WBBSE Class 8 Structure of Matter very short answer questions

Question 7. What is the fourth state of matter?
Answer:

Plasma is the fourth state of matter.

Question 8. Which is the heaviest sub-atomic particle present within an atom?
Answer:

A neutron is the heaviest sub-atomic particle present within an atom.

Question 9. What is the approximate temperature at the core of the sun?
Answer:

The temperature at the core of the sun is approximately 1 crore degree centigrade (107°C).

Question 10. What is the name of a chemical bond formed by the sharing of electrons between two atoms?
Answer:

Covalent bond.

Read And Learn More WBBSE Solutions For Class 8 School Science Very Short Answer Type Questions

Question 11. Name two ionic compounds.
Answer:

Ionic Compounds:

Sodium chloride (NaCI) and sodium hydroxide (NaOH) are two ionic compounds.

Question 12. Name two covalent compounds.
Answer:

Covalent Compounds:

Water (H2O) and hydrogen sulfide (H2S) are two covalent compounds.

Question 13. Under which condition an ionic compound conduct electricity?
Answer:

When fused or molten or when dissolved in water, an ionic compound can conduct electricity.

Very short answer questions on elements and compounds for Class 8

Question 14. What is the valency of hydrogen?
Answer:

The valency of hydrogen is 1.

Question 15. Give an example of a metal that can exhibit more than one valency.
Answer:

Fe is a metal that can exhibit two different valencies.

Question 16. When it is in ferrous form (Fe[Why an atom is uncharged?
Answer:

The atom consists of three types of sub-atomic particles – neutron (uncharged), proton (positively charged), and electron (negatively charged).

Since the number of protons and the number of electrons in an atom is the same, so there> is no net charge in the atom and the atom is uncharged.]

We know that “like” charges repel each other. If that is the case then positively charged protons within the nucleus must repel each other] ) its valency is 3.

Question 17. Give an example of a positively charged radical.
Answer:

(NHJ+ is a positively charged radical.

Question 18. Indicate the valency of different elements present in nitrogen trichloride.
Answer:

In NCI3N is the central atom with valency 3 and the valency of H is 1.

Question 19. Identify the central atom in PCI2 and CCI4. 
Answer:

The central atom in PCI2 is P (phosphorous) and the central atom in CCl4 is C (carbon).

WBBSE Chapter 2 structure of matter answers

Question 20. What is the number of protons and neutrons in ™Na?
Answer:

Given:

™Na

The number of neutrons is (23 – 11) = 12 and the number of protons is 11 in 23 11 Na.

Question 21. What is the number of protons and neutrons in 3517 Cl?
Answer:

Given:

3517 Cl

The number of neutrons is (35 – 17) = 18 and the number of protons is 17 in 35 15 cl.

Question 22. What type of chemical bonds are present in a solid compound which has a high melting point, and does not conduct electricity in the solid state but becomes a good conductor in the molten state?
Answer:

Ionic bond.

Question 23. How many covalent bonds are there in NH3 molecules?
Answer:

Given:

NH3 molecules

3 covalent bonds.

Structure of matter concepts with very short answers for Class 8

Question 24. An ion of an element has two unit positive charge. The mass number and number of neutrons of the element are 27 and 14 respectively. How many electrons are there in the ion?
Answer:

Given:

An ion of an element has two unit positive charge.

The mass number and number of neutrons of the element are 27 and 14 respectively.

Mass number, A =27

Number of neutrons = 14.

∴ Atomic number, Z = 27 -14 = 13

Since the ion has two unit positive charge, so the number of electrons in the ion = 13 – 2 = 11.

Question 25. Which one is covalent and which one is an ionic compound among PH3 and AICI3?
Answer:

  1. Covalent compound: PH3
  2. Ionic compound: AlC2

WBBSE Class 8 Science practice very short answer questions on elements and compounds

Question 26. Name one electropositive compound radical and one elemental radical.
Answer:

Electropositive compound radical: NH+4

Elemental radical: Cl–

Question 27. The atom of element X has 5 electrons in the 2nd shell. What is the atomic number of X?
Answer:

Given:

The atom of element X has 5 electrons in the 2nd shell.

Atomic number of X = 2 + 5 = 7.

 

 

 

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