Chemistry Periodic Table Exercise5a
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Q1 What is the need for classification of elements?
Q2 What was the basis of the earliest attempts made for classification and grouping of elements?
Q3 (a) A, B and C are the elements of a Dobereiner’s triad. if the atomic mass of A is 7 and that of C is 39, what should be the atomic mass of B?
(b) Why was Dobereiner’s triad discarded?
Q4 Explain ‘Newland’s law of Octaves.’ Why was the law discarded?
Q5 Did Dobereiners triads also exist in the columns of Newland’s Octaves? Compare and find out.
Q6 (a) Lithium. sodium and potassium elements were put in one group on the basis of their similar properties. What are those similar properties
(b) The elements calcium, strontium and barium were put in one group or family on the basis of their similar properties. Whit were those similar properties?
Q7 (a) What was Mendeleev’s basis for classification of elements?
(b) Mendeleev’s contributions to the concept of a periodic table laid the foundation for the Modern Periodic Table. Give reasons.
Q8 State Mendeleev’s periodic law.
Q9 Use Mendeleev’s periodic Law to predict the formula of
(a) hydrides of carbon and silicon
(b) Oxides of potassium, aluminium and barium
Q10 Which group of elements was missing from Mendeleev’s original periodic table ?
Q11 State the merits of Mendeleev’s classification of elements.
Q12 Why did Mendeleev leave some gaps in his periodic table of elements? Explain your answer with an example.
Q13 The atomic number of an element is more important to the chemist than its relative atomic mass. Why?
Q14 Consider the following elements: Be, Li, Na, Ca, K. Name the elements of (a) same group (b) same period.
Q15 (a) Name an element whose properties were predicted on the basis of its position in Mendeleev’s periodic table.
(b) Name two elements whose atomic weights were corrected on the basis of their positions in Mendeleev’s periodic table.
(c) How many elements were known at the time of Mendeleev’s classification of elements?
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