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

What are elements containing the same number of protons but different number of neutrons called?

  1. Isotopes

  2. Isobars

  3. Compounds

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

Isotopes are atoms of the same element with identical proton counts but different neutron counts. This gives them the same chemical properties but different atomic masses. Isobars have same mass number, compounds are combinations of elements, and allotropes are different structural forms of the same element.

Multiple choice

Elements present in equanil are

  1. C and H

  2. C, H and O

  3. C, H, O and N

  4. C, H, O, N and S
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Equanil (meprobamate) has the chemical formula C4H12CaN2O4 as the calcium salt, containing Carbon, Hydrogen, Oxygen, and Nitrogen. The presence of nitrogen is indicated by the 'amate' suffix (carbamate). Carbon and Hydrogen alone (A) is insufficient, C-H-O (B) lacks the nitrogen, and C-H-O-N-S (D) incorrectly adds sulfur.

Multiple choice

Which of the following is an element?

  1. Ruby

  2. Sapphire

  3. Emerald

  4. Diamond

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Diamond is pure carbon (an element). Ruby (Al2O3 with Cr), Sapphire (Al2O3 with Ti/Fe), and Emerald (Be3Al2Si6O18 with Cr) are all compounds or minerals with multiple elements.

Multiple choice

Two or more forms of a chemical element having different physical properties but rising to identical chemical compounds are called

  1. allotropes

  2. isotopes

  3. isomers

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

Allotropes are different structural forms of the same element with different physical properties (like diamond and graphite for carbon), but they form identical chemical compounds because they are the same element. Isotopes differ in mass, isomers have same formula but different structure, and isotones have same neutron count.

Multiple choice

Electronic configuration in ground state of Cu is

  1. 1s2 2s2 2p6 3s2 3p6 4s2 3d9

  2. 1s2 2s2 2p6 3s2 3p6 4s2 3d8

  3. 1s2 2s2 2p6 3s2 3p6 4s1 3d9

  4. 1s2 2s2 2p6 3s2 3p6 4s1 3d10

  5. 1s2 2s2 2p6 3s2 3p6 4s2 3d10
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Correct option. Completely filled d orbitals are stable. 29Cu: 1s2 2s2 2p6 3s2 3p6 4s1 3d10

Multiple choice

If the values of four quantum numbers n = 4, l = 0, m = 0 and s = +1/2, the element is

  1. K

  2. Na

  3. Cl

  4. Al

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

n = 4 and l = 0 represent 4s orbital. Since  it is valence electron, so the element belongs to s-block and 4th period of periodic table.
Out of five elements given in options, only two elements belong to s-block, i.e.  Na and K. Give quantum number data for the valence electron fits for sodium, K because it belongs to 4th period.

Multiple choice

The four most common elements in living organisms in order are

  1. Carbon, hydrogen, oxygen, nitrogen

  2. Hydrogen, oxygen, carbon, nitrogen

  3. Hydrogen, carbon, oxygen, nitrogen

  4. Carbon, oxygen, hydrogen, nitrogen
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In living organisms, the four most common elements by number of atoms are: Hydrogen (most abundant), followed by Oxygen, Carbon, and Nitrogen. This order (H > O > C > N) reflects their abundance in biological molecules like water, proteins, carbohydrates, and nucleic acids. Option C correctly lists them in this order by atomic count.