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Which of the following statements best defines the Modern Periodic Law?

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Free Technical Assistant( Kerala Drugs Control ) Practice Questions

Kerala Public Service CommissionRecruitment for the post of Technical Assistant in Kerala Drugs Control Department. The role involves scientific duties with a pay scale of ā‚¹35,600 - 75,400. Direct recruitment with age limits and qualification criteria apply.Direct RecruitmentDegree in Science with Chemistry required

Try 15 free syllabus-aligned practice questions for the Technical Assistant( Kerala Drugs Control ) exam. Each question includes instant feedback so you can learn as you go. No sign-up required.

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Q1. Which of the following statements best defines the Modern Periodic Law?

  1. Properties of elements are a periodic function of their atomic masses.
  2. Properties of elements are a periodic function of their atomic numbers.
  3. Elements are arranged in order of increasing density.
  4. Elements are grouped based on their physical states at room temperature.

Q2. The atomic number of an element is 20. Using the Modern Periodic Law, predict the group and period of this element in the periodic table.

  1. Group 2, Period 4
  2. Group 18, Period 3
  3. Group 1, Period 4
  4. Group 16, Period 4

Q3. Which factor primarily causes the atomic radius to decrease when moving from left to right across a period in the periodic table?

  1. Increase in number of electron shells.
  2. Increase in effective nuclear charge without significant increase in shielding.
  3. Decrease in nuclear charge.
  4. Increase in electron-electron repulsion in the outer shell.

Q4. Which of the following best explains the general trend in atomic radii across a period in the modern periodic table?

  1. Atomic radius increases due to increasing number of protons.
  2. Atomic radius decreases due to increasing effective nuclear charge.
  3. Atomic radius remains constant because electron shielding is unchanged.
  4. Atomic radius increases due to addition of electron shells.

Q5. Calculate the effective nuclear charge (Zeff) experienced by the outermost electrons of Mg2+ ion, given that Mg has atomic number 12 and the shielding constant (S) for the 10 electrons is approximately 10. Use Zeff = Z - S.

  1. 2
  2. 10
  3. 12
  4. 22

Q6. Consider two elements X and Y where X has atomic number 15 and Y has atomic number 16. According to the Modern Periodic Law, which of the following is true about their chemical properties?

  1. They have completely different chemical properties because their atomic masses differ.
  2. They have similar chemical properties because they are in the same group.
  3. They have different chemical properties because they belong to different groups.
  4. Their chemical properties depend only on their physical states.

Q7. Consider two elements, X and Y, in the same group of the periodic table where Y is below X. Which statement correctly compares their atomic radii?

  1. Element X has a larger atomic radius than element Y.
  2. Element Y has a larger atomic radius than element X.
  3. Both elements have the same atomic radius.
  4. Atomic radius depends only on the number of protons, so cannot be compared.

Q8. Calculate the approximate atomic radius of an element if the effective nuclear charge (Z_eff) experienced by its outermost electron is 5 and the principal quantum number (n) is 3, using the simplified formula: Atomic radius āˆ nĀ² / Z_eff. Which of the following values is closest?

  1. 1.8 (arbitrary units)
  2. 2.4 (arbitrary units)
  3. 3.6 (arbitrary units)
  4. 5.0 (arbitrary units)

Q9. Calculate the energy required to remove 2 moles of electrons from 2 moles of gaseous sodium atoms if the first ionization enthalpy of sodium is 496 kJ/mol.

  1. 496 kJ
  2. 992 kJ
  3. 248 kJ
  4. 1984 kJ

Q10. Which of the following best explains why ionization enthalpy decreases down a group despite increasing nuclear charge?

  1. Increase in atomic radius and electron shielding
  2. Decrease in number of electron shells
  3. Increase in effective nuclear charge
  4. Decrease in nuclear charge

Q11. In a hypothetical scenario, if the shielding effect in a period increased significantly while the nuclear charge remained constant, what would be the expected trend in atomic radii across that period?

  1. Atomic radius would increase across the period.
  2. Atomic radius would decrease across the period.
  3. Atomic radius would remain constant across the period.
  4. Atomic radius would first increase then decrease across the period.

Q12. Which of the following factors primarily causes the ionization enthalpy to increase across a period in the modern periodic table?

  1. Increase in atomic radius
  2. Increase in effective nuclear charge
  3. Increase in electron shielding
  4. Decrease in nuclear charge

Q13. Arrange the following factors in order of their influence on ionization enthalpy from most to least significant:1. Effective nuclear charge2. Atomic radius3. Electron shielding4. Subshell configuration stability

  1. 1 > 2 > 3 > 4
  2. 2 > 1 > 4 > 3
  3. 3 > 1 > 2 > 4
  4. 4 > 3 > 2 > 1

Q14. Which of the following trends correctly describes the variation of first ionization enthalpy across a period in the modern periodic table?

  1. It decreases from left to right across a period
  2. It remains constant across a period
  3. It generally increases from left to right across a period
  4. It fluctuates randomly with no trend

Q15. Which factor primarily causes the decrease in ionization enthalpy down a group in the periodic table?

  1. Increase in nuclear charge
  2. Increase in atomic radius and shielding effect
  3. Decrease in number of electrons
  4. Increase in effective nuclear charge
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