The statement that is not correct for the periodic classification of elements is:
Correct answer: C. The first ionization energies of elements along a period do not vary in a regular manner with increase in atomic number.
- A. The properties of elements are the periodic functions of their atomic numbers.
- B. Non-metallic elements are lesser in number than metallic elements.
- C. The first ionization energies of elements along a period do not vary in a regular manner with increase in atomic number.
- D. For transition elements, the d-sub shells are filled with electrons monotonically with increase in atomic number.
Explanation
The correct answer is Option C: The first ionization energies of elements along a period do not vary in a regular manner with increase in atomic number. This is incorrect because ionization energy generally does increase across a period, not irregularly, due to the increasing nuclear charge. Option A is correct because it reflects the periodic law, which states that the properties of elements are periodic functions of their atomic numbers. Option B is correct in stating that non-metallic elements are fewer in number compared to metallic elements.Option D, while mostly correct, oversimplifies the filling of d-subshells in transition elements, as there are some exceptions due to the similar energies of nearby orbital levels. However, it generally follows a sequential pattern.
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About Periodic Properties and Trends
Periodic properties arise from electron configuration and effective nuclear charge, producing trends in atomic and ionic radius, ionization energy, electron affinity, electronegativity, metallic character and reactivity. Comparisons run across periods and down groups, with attention to common exceptions. The topic also relates these trends to the behavior of s-block and p-block elements.
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