CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Very Short Answer Questions

CBSE Class 10 Science Chapter 5 Periodic Classification Of Elements Very Short Answer Questions

Question 1. Where would you expect to find the element with atomic number 18 in the periodic table?
Answer: An element with atomic number 18 will lie in the 18th group and the 3rd period of the periodic table

Question Who classified the elements based on fundamental properties of elements like atomic mass?
Answer: Mendeleev.

Question 3. An element X’ belongs to the second group of the periodic table. What is the formula of sodium chloride?
Answer: XCl₂.

Question 4. State modern periodic law of classification of elements.
Answer: The properties of elements are a periodic function of their atomic number.

Question 5. Name the elements present in the first period.
Answer: Hydrogen and Helium.

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Question 6. An element has the atomic number 16. To which group and period does it belong?
Answer:

K – 2

L – 8

M – 6

A(16) = 2, 8, 6

Period = 3rd

Group = 10 + 6

= 16.

Question 7. Out of and K, which will have a stronger metallic character and why? 
Answer:

Potassium (K) will have a stronger metallic character than lithium (Li) because as we move from top to bottom in a group, the size increases, which increases the ease of liberation of electrons.

Question 8. Write the atomic number of two elements X’ and ‘Y’ having electronic configurations of 2, 8, 2 and 2, 8, 6 respectively.
Answer:

X -12(2 + 8 + 2)

Y- 16 (2 + 8 + 6)

Question 9. A metal ‘M’ belongs to the 13th group in the modern periodic table. Write the valency of the metal.
Answer:

The valency of the metal is 3.

Question 10. Chlorine, bromine, and iodine from a Dobereiner’s triad. The atomic masses of chlorine and iodine are 35.5 and 126.9 respectively. Predict the atomic mass of Bromine.
Answer:

Atomic mass = \(\frac{35.5+126.9}{2}\)

= \(\frac{162.4}{2}\)

= 81.2

Question 11. Find the atomic number of the element whose electronic configuration is 2, 8, 5.
Answer:

Atomic number = 2 + 8 + 5

15 = no. of electrons.

Question 12. List any two properties of the element belonging to the first group of the modern periodic table.
Answer:

1. Elements are monovalent.
2. Elements are metal/electropositive.
3. Elements form basic oxides, (any two)

Question 13. Write two reasons responsible for the late discovery of noble gases.
Answer:

They are less available in nature.

They do not react, i.e., inert.

Question 14. What are the names of group 1 and group 17 elements?
Answer:

1. Group 1- Alkali metals
2. Group 17- Halogens.

Question 15. The atomic numbers of 3 elements A, B, and C are 12, 18, and 20 respectively. State and give a reason for which 2 elements will show similar properties.
Answer:

A and C, as they belong to the same group, as they have the same number of valence electrons.

Question 16. Predict the maximum number of valence electrons possible for elements in the first period of the periodic table.
Answer: 2 (in Helium)

Question 17. How many vertical columns are there in the modern periodic table, and what are they called?
Answer:

18 vertical columns are present and they are called groups.

Question 18. Give the number of elements in the 2nd and 5th periods in the modern periodic table.
Answer:

2nd period- 8 elements

5th period- 18 elements

Question 19. Write the formula that determines the maximum number of electrons that the shell of an atom can accommodate.
Answer:

2n², where W is some shells.

Question 20. Why was the system of classification of elements into triads not found suitable?
Answer:

Because all the elements discovered at that time could not be classified into triads.

Question 21. Which can gain electrons easily O or F?
Answer:

F can gain electrons more easily because it is smaller.

Question 22. Name any two pairs of elements that were adjusted by Newlands in the same slot.
Answer:

1. Cobalt and Nickel
2. Caesium and lanthanum

Question 23. Arrange the following metals in decreasing order of their atomic size. Ca, Mg, Be, Ba.
Answer:

Ba > Ca > Mg > Be

Question 24. What would be the nature of oxides formed by the elements on the right-hand side of the periodic table?
Answer: Acidic

Question 25. On what basis we can classify elements?
Answer: Similarity in properties.

Question 26. What was the earliest attempt to classify elements?
Answer: They were classified as metals and non-metals.

Question 27. What is a metalloid? Name any two of them.
Answer:  The element which shows some properties of both metals and non-metals is called a metalloid. Example: Silicon and Boron.

Question 28. Name any two elements which were discovered later after Mendeleev’s periodic table.
Answer:  Gallium and germanium

Question 29. Which is smaller, Carbon or Nitrogen?
Answer: Nitrogen

Question 30. What is the place of metalloids in the periodic table?
Answer: In the middle.

Question 31. What did Mendeleev use the criteria in creating his periodic table?
Answer: 

The criteria used by Mendeleev to create his periodic table was a Periodic Law, as stated below:  “The physical and chemical properties of elements are periodic functions of their atomic masses”.

Question 32.

1. Lithium, sodium, and potassium are all metals that react with water to liberate hydrogen gas. Is there any similarity in the atoms of these elements?
2. Helium is an unreactive gas and neon is a gas of extremely low reactivity. What, if anything, do their atoms have in common?

Answer:

Yes, lithium, sodium, and potassium are similar because these contain one electron in their outermost shell. The atoms of helium and Neon have their outermost shell filled and are thus unreactive gases.

Question 33. In the Modern Periodic Table, which are the metals among the first ten elements?
Answer:  Li, and Be are metals.

Question 34. By considering their position in the Periodic Table, which one of the following elements would you expect to have maximum metallic characteristics? Ga Ge As Se Be
Answer:

As elements on the left side of the periodic table are more metallic, therefore, Beryllium (Be) has the maximum metallic character as it is found on the extreme left side of the periodic table.

Question 35. Why K is more reactive than Li?
Answer: K has a larger atomic size, therefore it can lose electrons due to less force of attraction between the nucleus and electrons.

Question 36. Write the formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by Mendeleev.
Answer: GeCl₄, GaCl₃.

Question 37. If an element is placed in group 14, what will be the formula and the nature of the bonding of its chloride?
Answer: XCl₄; Covalent bonding.