Q2. Consider the following statements with regard to periodic classification of elements. [1]
A. In Modern Periodic Table, the isotopes of an element having different mass numbers are
put at one place in the same group.
B. Elements in Mendeleev's Periodic Table are arranged on the basis of increasing atomic
numbers.
C. Elements in the Modern Periodic Table are arranged on the basis of increasing mass
numbers.
D. In the Modern Periodic Table, nickel of a lower mass number is kept after cobalt of a
higher mass number.
The correct statements are
(a) Aand B (b) B and C (c) C and D (d) A and D
Answers
Answer:
A. All isotopes of an element have same number of protons and hence they have the same atomic number. Hence, they can be placed at the same position in the periodic table.
B. According to Mendeleev's periodic law, the elements were arranged in the periodic table in the order of increasing atomic number.
C. The periodic table of elements arranges all of the known chemical elements in an informative array. Elements are arranged from left to right and top to bottom in order of increasing atomic number. Order generally coincides with increasing atomic mass. The rows are called periods
D. The atomic numbers of cobalt and nickel are 27 and 28 respectively. Hence, cobalt with a lower atomic number is placed before nickel in the modern periodic table.
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