Chemistry

Periodic Classification and Elements

1,176 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 statements is/are wrong?

(A) The shape of an atomic orbital depends on the azimuthal quantum number. (B) The energy of the electron in an atomic orbital of multielectron atom depends on principal quantum number. (C) The number of degenerate atomic orbitals of one type depends on the values of principal azimuthal and magnetic quantum number.

  1. Only (A)

  2. Only (B)

  3. Only (A) and (B)

  4. Only (B) and (C)

  5. Only (A) and (C)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option (B) is not correct because energy depends upon principal as well as azimuthal quantum numbers and option (C) is not correct because the number of degenerate orbitals depends upon the value of azimuthal quantum number.

Multiple choice

Which of the following is a drawback of the modern periodic table?

  1. Position of lanthanides and actinides

  2. Position of elements in relation to electric configuration

  3. Regular variation in properties along a period

  4. Position of halogens
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

It fails to accommodate lanthanides and actinides in the main body of periodic table.

Multiple choice

Which of the following properties was adopted as the basis of the modern periodic table?

  1. Atomic mass

  2. Atomic radius

  3. Density

  4. Atomic number
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The earlier attempts at classification of elements was based on atomic masses. Later on, it was found that atomic number is a more appropriate parameter to determine the properties of an element. Therefore, in the modern periodic table, elements are arranged in the increasing order of their atomic number. 

Multiple choice

At which element did Newlands’ arrangement of elements end?

  1. Helium

  2. Selenium

  3. Tin

  4. Thorium
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Newlands, an English scientist, arranged the elements according to their increasing atomic masses. He started with hydrogen (Atomic mass = 1 u), the element having the least atomic mass and ended with thorium, which was the 56th element.

Multiple choice

Which of the following groups of elements, discovered later, could be placed in Mendeleev’s periodic table without disturbing the existing order of groups?

  1. Alkali metals

  2. Alkaline earth metals

  3. Noble gases

  4. Halogens
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The noble gases like helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn) were not known when Mendeleev gave his periodic table. These gases were discovered later on because they are inert and are present in extremely low concentration in our atmosphere. But, it was the strength of Mendeleev’s periodic table that these gases, when discovered, could be placed in a new group called zero group, without disturbing the existing order. Halogens (F, Cl, Br, I), alkali metals (Li, Na, K, Rb, Cs) and alkaline earth metals (Be, Mg, Ca, Sr, Ba) were already discovered when Mendeleev gave his periodic table. So, they were already occupying specific positions in his periodic table.

Multiple choice

The existence of which of the following elements was predicted by Mendeleev before it was actually discovered?

  1. Scandium

  2. Titanium

  3. Cesium

  4. Iodine
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Mendeleev left some gaps in his periodic table for some undiscovered elements. Mendeleev boldly predicted that these elements would be discovered later. He even predicted the properties of these unknown elements and named these elements by prefixing a Sanskrit word ‘eka’ to the name of the preceding element in the same group, e.g. eka–boron for scandium, eka-aluminium for gallium and eka-silicon for germanium. Titanium, cesium and iodine were already discovered when Mendeleev gave his periodic table. So, option (1) is the correct answer.

Multiple choice

What is the cause of periodicity in properties of elements?

  1. Recurrence of similar electronic configuration

  2. Recurrence of similar atomic size

  3. Recurrence of similar atomic weight

  4. Recurrence of similar physical character
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Periodicity occurs due to recurrence of similar electronic configuration.