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

The atomic number of an element signifies the number of

  1. protons in the nucleus

  2. electrons in the nucleus

  3. electrons in the extranucleur part

  4. protons in the extranucleur part

  5. electrons and protons in the nucleur part
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct answer as the atomic number of an element signifies the number of protons.

Multiple choice

Which of the following elements is not a part of any of Dobereiner’s triads?

  1. K

  2. F

  3. Cl

  4. I
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Dobereiner, when elements of a given triad are arranged on the basis of increasing atomic masses, the atomic mass of the middle element is roughly the mean or average of the atomic masses of the other two elements. Dobereiner gave only three traids - (Li, Na, K); (Cl, Br, I) and (Ca, Sr, Ba).

Multiple choice

Compounds of which of the following elements were used as a standard reference by Mendeleev to classify elements?

  1. Hydrogen and oxygen

  2. Carbon and hydrogen

  3. Oxygen and carbon

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

Mendeleev classified the elements according to their increasing atomic masses in horizontal rows in such a way that the elements with similar chemical properties (i.e. elements with similar formulae of oxides and hydrides) fell in the same vertical column. He preferred only oxygen and hydrogen because oxygen and hydrogen form bond with almost all elements.

Multiple choice

Which of the following elements was incorrectly placed in Mendeleev's periodic table?

  1. Boron

  2. Helium

  3. Aluminium

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

Mendeleev's periodic law states that poperties  of elements are periodic functions of their atomic masses. Therefore the elements are arranged in the increasing order of their atomic masses.  However Mendeleev placed cobalt before nickel eventhough it has a slightly higher mass than nickel. 

Multiple choice

An element X has 7 electrons in its L shell. Which of the following statements are true about element X?

I. It belongs to period 9 of modern periodic table. II. Its atom contains 9 protons. III. It has a valency of 7. IV. Its atom can accept an electron to acquire noble gas configuration.

  1. I and II

  2. II and Ill

  3. III and IV

  4. Il and IV
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Element X, having atomic number 9, contains 9 protons and its valence shell contains 7 electrons. To acquire noble gas configuration, it can accept one electron.

Multiple choice

An element has configuration 2, 8, 1. It belongs to

  1. 1st group and 3rd period

  2. 3rd group and 1st period

  3. 1st group and 8th period

  4. 17th group and 3rd period
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The number of shells tells the period and the number of electrons in the last valence shell tells the group.