Extra Questions for Class 10th: Ch 5 Periodic Classification of Elements (Science) Important Questions Answer Included

Very Short Answer Questions (VSAQs): 1 Mark

Q1. Why was the system of classification of elements into triads not found suitable ? 
It is because all the elements discovered at that time could not be classified into triads.

Q2. What is the total number of period in periodic table?
There are seven periods in modern periodic table.

Q3.  According to which periodic table, every eight element repeat its property?
Newlands Octave

Q4. Why Doberiner triad theory failed?
Only three triads were discovered. 

Q5. Which  element was named as Eka–aluminium earlier?

Short Answer Questions-I (SAQs-I): 2 Marks

Q1. How does the electronic configuration of an atom of an element relate to its position in the modern periodic table ? Explain with one example.


The position of elements depends upon number of valence electrons which depend upon electronic configuration. Those elements which have same valence electrons, occupy same group. Those elements which have one valence electron belong to group 1.  Elements which have two valence electrons belong to group 2. Period number is equal to the number of shells. Example : Atomic number of sodium (Na) is 11, so electronic configuration will be 2, 8, 1. Sodium has one valence electron in valence shell so it belongs to group 1. As sodium has three shells, so it belongs to 3rd period.

Q2.  Wrtie two achievements of Mendeleev periodic Table?


Two achievements are
(i)He inverted some elements that were in ascending order to make sure elements with similar behavior come in same group. For example cobalt was put before Nickel.
(ii)Scope for new elements: He gave the name to undiscovered elements like , Eka–aluminium to Galium which was  discovered latter.

Q3. State the modern periodic law for classification of elements. How many (a) groups and (b) periods are there in the modern periodic table ? 


"Properties of elements are the periodic function of their atomic number." (a) There are 18 groups. (b) There are 7 periods in the modern periodic table.

Q4. Give an account of the process adopted by Mendeleev for the classification of elements


Elements having similar properties were placed in the same group.
Elements were automatically arranged in increasing order of their atomic masses except few discrepancies were there.

Short Answer Questions-II (SAQs-II): 3 Marks

Q1.(i)  State the main aim of classifying elements. Which is the more fundamental property of elements that is used in the development of Modern Periodic Table? 
(ii) Name and state the law based on this fundamental property. On which side of the periodic table one can find metals, non-metals and metalloids? 


(i) Aim of classification : Systematic study of the known elements based on certain similarities in physical and chemical properties.
(ii) Basic property : Atomic number. Properties of the elements are a periodic function of their atomic numbers. (iv) Metals on the left. 
(iii) Non—metals on the right, Metalloids at the border of metals and beginning of non-metals.

Q2. (a) Predict which of the following elements will form cation and will form anions?
(i) Na, 
(ii) Al, 
(iii) Cl,
(iv) O
(b) Name two elements that are inert in nature.


(a) Cations are Na and Al (Sodium and Aluminium) Anions are Cl and O (Chlorine and Oxygen) 
(b) Inert elements are He and Ne (Helium and Neon)

Q3. What are metalloids? (b) Name any four metalloids? 


(a) Elements which are intermediate in properties between metals and non-metals are called metalloids. In periodic table, they act as border between metals and non-metals.
(b) Boron, silicon, germanium and arsenic.

Q4. How does the electronic configuration of an atom relates to its position (period and group) in the modern periodic table ? 
(b) Would you place the two isotopes of chlorine, CI - 35 and Cl - 37, in different slots because of their different atomic masses or in the same slot because their chemical properties are the same ? Justify your answer. 


(a) In the periodic table, elements are placed according to their atomic number. If an element has only one shell in its electron configuration, it is placed in the first period. If the element has two shells then it is placed in the second period. and so on. Vertical columns in the periodic table are called groups. There are eighteen groups and in a group all the elements have same number of valence electrons.
 (b) No, Cl-35 and Cl-37 will be placed in same slot. The modern periodic table is based on atomic number, not on atomic mass. Since, both Cl-35 and Cl-37 have same atomic number, hence they are placed in same slot.

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