Which of the following represents the correct order of increasing first ionization enthalpy for Ca, Ba, S, Se and Ar?

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Engineering

Chemistry

Shielding Effect and Penetration Effect

Atomic and Ionic Radius

Ionisation Energy

Question

Which of the following represents the correct order of increasing first ionization enthalpy for Ca, Ba, S, Se and Ar?

A

Ca < Ba < S < Se < Ar

B

Ba < Ca < Se < S < Ar

C

S < Se < Ca < Ba < Ar

D

Ca < S < Ba < Se < Ar

Among Ca, Ba, S, Se , Ar

Ba has minimum Ionisation energy and Ar has highest ionisation energy

Ba < Ca < Se < S < Ar

First ionization enthalpy is the energy required to remove the most loosely bound electron from an isolated gaseous atom. It depends on atomic size, effective nuclear charge, and stability of electronic configuration.

Key factors affecting ionization enthalpy:

Atomic size: Larger atoms have lower ionization enthalpy because the outermost electron is farther from the nucleus and experiences less attraction.
Effective nuclear charge (Z_eff): Higher effective nuclear charge increases ionization enthalpy because electrons are more strongly attracted to the nucleus.
Stability of configuration: Half-filled or fully filled orbitals are more stable, requiring higher energy to remove an electron.

Step-by-step analysis of the given elements:

Step 1: Compare elements in the same group

Group 2 elements: Ca (atomic number 20) and Ba (atomic number 56). Ionization enthalpy decreases down a group due to increasing atomic size. So, Ba < Ca.

Step 2: Compare elements in the same period

Period 4 elements: Ca, Se (atomic number 34). Ionization enthalpy generally increases across a period due to decreasing atomic size and increasing effective nuclear charge. So, Ca < Se.

Step 3: Compare S and Se (Group 16)

Sulfur (S, atomic number 16) and Selenium (Se, atomic number 34). Ionization enthalpy decreases down the group, so S > Se.

Step 4: Consider Argon (Ar)

Argon (Ar, atomic number 18) has a stable noble gas configuration (fully filled orbitals), so it has the highest ionization enthalpy among these elements.

Step 5: Combine all comparisons

From the above: Ba < Ca < Se < S < Ar

Thus, the correct order is Ba < Ca < Se < S < Ar.

Final Answer: The correct option is Ba < Ca < Se < S < Ar.

Related Topics

Periodic Trends: Ionization enthalpy, electron affinity, electronegativity, and atomic radius show predictable trends across periods and down groups in the periodic table.

Electronic Configuration: The arrangement of electrons in orbitals influences chemical properties and stability, affecting ionization energy.

Formulae

Ionization enthalpy is measured in kJ/mol. While there's no simple formula, it can be calculated using quantum mechanical models, but typically, values are determined experimentally and compared using periodic trends.