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#element identification

14 public questions tagged with this topic.

A solid has a molar specific heat capacity of 24.9 J mol⁻¹ K⁻¹ . Which element could it be?

**Thermal equilibrium** achieved when temperatures equal, zeroth law allows definition of temperature, quasi-static process approximates equilibrium at each step, enabling calculation of work as area under P-V curve, reversible processes are quasi-static without dissipative effects. Tungsten has C = 24.9 J mol⁻¹ K⁻¹ . Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal W = n R T ln(V₂/V₁), adiabatic P V^γ = const and η = 1 - T_c/T_h, evaluation yields Tungsten, consistent with thermodynamic laws and energy conservation.

Ref: NCERT > Physics Book > Thermodynamics > Zeroth Law Thermal Equilibrium and Quasi-static

100

Which of the following is a chalcogen?

Chalcogens are group 16 elements. Te (group 16) is a chalcogen, while As (group 15), Br (group 17), and Ge (group 14) are not.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Nomenclature of Elements with Atomic Number >100

100

Which of the following elements is a halogen?

Halogens belong to group 17. Among O, S, Se, and Br, only Br is in group 17, making it a halogen.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Nomenclature of Elements with Atomic Number >100

Which element has the ground state electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d³ 4s²?

This configuration (Z=23) corresponds to V (period 4, group 5), with 3d³ 4s², distinguishing it from Ti (3d² 4s²), Cr (3d⁵ 4s¹), or Mn (3d⁵ 4s²).

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Genesis of Periodic Classification - Dobereiner Newlands Mendeleev

Which element has the ground state electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹?

This configuration (Z=24) corresponds to Cr, an exception due to the stability of half-filled 3d⁵, unlike Mn (3d⁵ 4s²), Fe (3d⁶ 4s²), or Co (3d⁷ 4s²).

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Electronic Configuration and Types of Elements - s p d f Blocks

Which element has the ground state electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²?

This configuration (Z=26) corresponds to Fe (period 4, group 8), with 3d⁶ 4s², distinguishing it from Mn (3d⁵ 4s²), Co (3d⁷ 4s²), or Ni (3d⁸ 4s²).

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Anomalous Properties and Second Period and Chemical Reactivity