Chemistry

Periodic Classification and Elements

1,092 Questions

Periodic classification organizes chemical elements based on atomic structure, periodic laws, and elemental properties. It covers historical classification systems, electron configurations, and periodic trends. Test takers preparing for chemistry sections will find these questions crucial for mastering fundamental element properties and atomic interactions.

Periodic table structureAtomic orbitalsElement identificationPeriodic laws

Periodic Classification and Elements Questions

Multiple choice

Which of the following observations posed a challenge to Mendeleev’s periodic law?

(a) Position of alkali metals (b) Position of isotopes (c) Anomalies of atomic weights and properties of elements (d) Placing of dissimilar elements in the same group

  1. Only (a)

  2. Only (b), (c) and (d)

  3. Only (b) and (c)

  4. Only (c) and (d)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Mendeleev, in his periodic table, arranged the elements according to their increasing atomic masses but gave priority to the similarity in the fomulas of the oxides and hydrides while groupig them. As a result at some places, an element with a greater atomic mass was placed before an element with a lower atomic mass. For example, Co (atomic mass = 58.93 u) was placed before Ni (atomic mass = 58.71 u), which challenged the law that Mendleeev gave, that the properties of elements are periodic funtions of their atomic masses. Moreover the isotopes of an element have different atomic masses, but could not be alloted separate places in the periodic table on account of the similarity in the formulas their oxides and hydrides.  Therefore, (c) and (d) posed a challenge to Mendeleev's periodic law.

Multiple choice

Which of the following are the discrepancies in Mendeleev's periodic table?

(a) He placed some alkali metals with coinage metals in the same group. (b) He placed dissimilar elements in the same group. (c) The atomic masses do not increase in a regular manner in going from one element to the next in the same period.

  1. Only (a) and (b)

  2. Only (a), (b) and (c)

  3. Only (a) and (c)

  4. Only (b) and (c)
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

All the statements given above were the discrepancies in Mendeleev's periodic table. 

Multiple choice

Electrons in the outer orbit are __________.

  1. nuclei

  2. waves

  3. valence

  4. holes

  5. shells
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Valence, also known as valency or valence number, is the number of valence bonds a given atom has formed or can form, with one or more atoms. For most elements the number of bonds can vary.

Multiple choice

Why is Newlands' method of classification of elements known as law of octaves?

  1. Because it could classify only eight elements

  2. Because every eighth element had the properties similar to the first

  3. Because the classification was based on the atomic masses of the element

  4. Because the elements were classified in eight groups
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Newlands' law of octaves, when the elements are arranged in order of increasing atomic weights, then every eighth element has properties similar to that of the first element.

Multiple choice

Which of the following statements is/are not true about Mendeleev's periodic table?

(a) He started his work with 65 elements known at that time. (b) He examined the relationship between the atomic masses of the elements and their physical and chemical properties. (c) Mendeleev gave a specific position to isotopes also in his periodic table.

  1. Only (a)

  2. Only (b)

  3. Only (c)

  4. Both (a) and (c)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Both a and c are wrong. Mendeleev classified the 56 known elements of his time. No separate slot was alloted to the isotopes in Mendeleev's periodic table.