Test: Periodic Classification of Elements (Easy)

15 Questions MCQ Test | Test: Periodic Classification of Elements (Easy)

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The nuclear charge of Li is:

Solution: As we know, an atomic number of Li is 3. So it contains 3 protons in the nucleus, So its nuclear charge is 3.

Which of the following is one of the major drawbacks of Mendeleev's periodic table?

Solution: The discovery of isotopes was one of the limitations of Mendeleev's periodic table. Since Mendeleev's periodic table was based on atomic masses of elements, isotopes should be placed in different columns despite the fact that they represent the same element. Novel gases were placed in a group of Mendeleev's periodic table called zero group.

With an increase in temperature by 10k, the rate of reaction becomes double. How many times the rate of reaction will be if the temperature is increased from 303 k to 353 k?

Solution: By increasing 10K temperature the rate of reaction becomes double. When temperature is increased from 303K to 353K, the rate increases in steps of 10o and has been made 5 times. Hence, the rate of reaction should increase 25 times ie, 32 times.

Name the element that first shows some visible metallic properties at room temperature.

Solution: The high ionization energy makes the element appear non-metallic while Iodine and astatine having low ionization energy display metallic properties and Iodine was the first element to show some physical properties of metals.

The properties of_________were predicted by Mendeleev before their isolation.

Solution: Mendeleev has the foresight to leave some gaps in the periodic table for 3 elements and these elements are discovered later and included in the table.

The number of elements known in Mendeleev's presented periodic table is:

Solution: In Mendeleev's periodic table, elements were arranged on the basis of the fundamental property, atomic mass, and chemical properties. During Mendeleev's work, only 63 elements were known.


The law of triads is not applicable to:

Solution: The law of triads does not apply to Ru, Rh, Pt.

Lanthanides belong to which period?

Solution: Lanthanides belong to 6th period. They start from atomic number 58 and ends in 71


In Mendeleev's periodic table, the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.69 amu. Reason for the same is that:

Solution: According to Mendeleev's classification, the properties of elements are the periodic function of their atomic masses and there is a periodic recurrence of elements with similar physical and chemical properties.

The law of triads was given by:

Solution: In the year 1829, Johann Wolfgang Dobereiner,a German scientist, was the first to classify elements into groups based on John Dalton's assertions. He grouped the elements with similar chemical properties into clusters of three called 'Triads'. The distinctive feature of a triad was the atomic mass of the middle element. When elements were arranged in order of their increasing atomic mass, the atomic mass of the middle element was approximately the arithmetic mean of the other two elements of the triad.

In order to fit elements into his table, Newlands adjusted three elements in the same slot, but also put some unlike elements in the same slot.

Solution: For example, cobalt and nickel were in the same slot and these were placed in the same column as fluorine, chlorine, and bromine which have very different properties than these elements. Iron, which resembles cobalt and nickel in properties, had been placed far away from these elements.

Mendeleev examined the relationship between_________and______for classification of elements.

Solution: When Mendeleev selected his work, 63 elements were known. He examined the relationship between the atomic masses of the elements and their physical and chemical properties. He observed that most of the elements get a place in a periodic table and were arranged in order of their increasing atomic masses.

Pair of element shaving same number of valence electrons is:

Solution: Atoms which are present in the same group of the periodic table will have same number of valence electrons. Hence Cl, I of group 17, Na, Ca group 1 and C, Ge group 14 have same valence electrons.

How many periods were there in Mendeleev's periodic table?

Solution: There are a total of 8 groups and 7 periods in the modified Mendeleev table.

What were the limitations of Mendeleev's periodic table?

Solution: LIMITATIONS OF Mendeleev's Periodic Table :
  • Position of Hydrogen => Position of hydrogen in the periodic table is Uncertain Because hydrogen is placed in 1 A group with Alkali metals.

  • Position of isotopes => isotopes haven't been given separate place in periodic table.

  • Cause of periodicity => Mendeleev could not explain the cause of periodicity.

  • Separation of similar elements => some dissimilar elements have been placed together