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

Modern periodic table is based on the atomic number of elements. Which of the following experiments proved the significance of the atomic number?

  1. Millikan's drop experiment

  2. Moseley's work on X-ray spectra

  3. Bragg's work on X-ray diffraction

  4. Discovery of X-ray roentgen
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Moseley was able to show that the frequencies of certain characteristic X-rays emitted from chemical elements are proportional to the square of a number which is close to the element's atomic number; a finding which supported van den Broek and Bohr's model of the atom in which the atomic number is the same as the number of positive charges in the nucleus of the atom.

Multiple choice

The screening effect of s orbital electron is

  1. greater than p, but lesser than d and f electrons

  2. lesser than p, d and f electrons

  3. greater than p, d and f electrons

  4. equal to p, d and f electrons
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Screening effect decreases in the order s > p > d > f.

Multiple choice

Which of the following statements is true?

  1. Atomic radii of elements decrease gradually from left to right.

  2. Metallic character increases across a period.

  3. Chemical reactivity increases and then decreases across a period.

  4. Chemical reactivity increases across a period.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Only statement in option (1) is correct. Atomic radii of elements decrease gradually from left to right because new electrons are added into the same shell and the effective nuclear charge increases across the period.

Multiple choice

The electronic configurations of four elements are given as follows:

  1. [Xe] 6s1 2. [Xe] 4f14 5d1 6s2 3. [Ar]4s24p5 4. [Ar]3d74s2

Which of the following statements about these elements is not correct?

  1. 1 is a strong reducing agent.

  2. 2 is a d-block element.

  3. 3 has high electron affinity.

  4. 4 shows variable oxidation state.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

[Xe] 4f14, 5d1, 6s2 is not a d-block element. It is lutetium and is present in lanthanide series. It is an f-block element.

Multiple choice

The successive ionisation energy values for an element 'X' are given below:

(i) 1st ionisation energy = 410 kJ mol-1 (ii) 2nd ionisation energy = 820 kJ mol-1 (iii) 3rd ionisation energy = 1100 kJ mol-1 (iv) 4th ionisation energy = 1500 kJ mol-1 (v) 5th ionisation energy = 3200 kJ mol-1

Find out the number of valence electrons for an atom of 'X'.

  1. 4

  2. 3

  3. 5

  4. 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The ionisation energy values for valence electrons are comparable. To remove electrons from inner shell, very high amount of energy is needed. Among the given values, the biggest jump is between IE4 and IE5. Hence, there are four valence electrons for an atom of 'X'.

Multiple choice

What is a chemical compound?

  1. A subatomic particle

  2. A combination of two protons and two electrons

  3. A combination of two or more chemical elements

  4. A mixture of two or more substances
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

fact