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Indian Navy 10+2 B.Tech Cadet Classification of Elements — practice questions

Explore 60 free Classification of Elements questions in Indian Navy 10+2 B.Tech Cadet Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Classification of Elements questions and exercises with answers

Showing questions 1–30 of 60.

Across a period from left to right, the atomic radius generally:Read the answer and worked solution →Which element has the highest first ionization energy in period 2?Read the answer and worked solution →The minimum energy required to remove an electron from the ground state of a hydrogen atom is:Read the answer and worked solution →According to VSEPR theory, the shape of a molecule is determined byRead the answer and worked solution →The hybridisation of carbon in methane (CH₄) isRead the answer and worked solution →What is the valency of an element with electronic configuration 2, 8, 3?Read the answer and worked solution →Which of the following elements does not lose an electron easily?Read the answer and worked solution →Arrange the following elements in the order of their decreasing metallic character Na, Si, Cl, Mg, AlRead the answer and worked solution →Arrange the following elements in the order of their increasing non-metallic character Li, O, C, Be, FRead the answer and worked solution →On moving from left to right in a period in the periodic table, the size of the atom.Read the answer and worked solution →Order the atomic models as they were proposedRead the answer and worked solution →Match each scientist to their modelRead the answer and worked solution →Match each model to what it could NOT explainRead the answer and worked solution →True or false: Rutherford's modelRead the answer and worked solution →True or false: Bohr's modelRead the answer and worked solution →Complete the reason Bohr's model failsRead the answer and worked solution →Which model does this belong to?Read the answer and worked solution →Match each quantum number to what it is calledRead the answer and worked solution →True or false: the quantum mechanical modelRead the answer and worked solution →Order the structure: from atom down to electronRead the answer and worked solution →Complete the (n + l) ruleRead the answer and worked solution →True or false: orbital energiesRead the answer and worked solution →Match each rule to what it forbids or requiresRead the answer and worked solution →Tap every statement Hund's rule requiresRead the answer and worked solution →The fundamental particlesRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Which principle is being described?Read the answer and worked solution →Flip and pair: symbol with meaningRead the answer and worked solution →

Worked practice questions

Across a period from left to right, the atomic radius generally:

  1. Decreases
  2. Remains constant
  3. Increases
  4. First increases then decreases
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Correct answer: A. Decreases

Atomic radius **decreases** from left to right across a period. Why: nuclear charge ($Z$) increases by 1 as you move right, pulling electrons closer. The added electron enters the same shell so screening barely increases — the net effect is stronger attraction and smaller radius. Across period 2: Li (152 pm) → Be → B → C → N → O → F (72 pm). Roughly halves. Down a group, atomic radius *increases* (electrons go into higher principal shells, further from nucleus).

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Which element has the highest first ionization energy in period 2?

  1. Carbon (C)
  2. Oxygen (O)
  3. Neon (Ne)
  4. Lithium (Li)
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Correct answer: C. Neon (Ne)

First ionization energy generally increases across a period because nuclear charge grows and atomic radius shrinks, making it harder to remove an outer electron. In period 2: Li (520) < Be (899) ≈ B (801) < C (1086) < N (1402) > O (1314) < F (1681) < **Ne (2081)** kJ/mol. Neon has the highest because it has a stable octet ($1s^2 2s^2 2p^6$, full $2p$). Removing an electron requires breaking that closed shell. Note two anomalies: B < Be (removing a $2p$ electron easier than $2s$) and O < N (paired $2p$ electron in O has extra repulsion).

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The minimum energy required to remove an electron from the ground state of a hydrogen atom is:

  1. $3.4\,\text{eV}$
  2. $13.6\,\text{eV}$
  3. $27.2\,\text{eV}$
  4. $1.51\,\text{eV}$
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Correct answer: B. $13.6\,\text{eV}$

Ionisation energy is the energy required to take the electron from $n = 1$ to $n = \infty$. $E_\infty - E_1 = 0 - (-13.6) = 13.6\,\text{eV}$. The value $27.2\,\text{eV}$ is the magnitude of the potential energy in the ground state, not the ionisation energy.

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