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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?

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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

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Q1. 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)

Q2. 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

Q3. Given the ionic radii of O2- (140 pm), F- (133 pm), and Na+ (102 pm), which of the following statements is true regarding their sizes?

  1. O2- is smaller than F- due to higher nuclear charge
  2. Na+ is the smallest because it has the highest positive charge
  3. F- is larger than O2- because it has fewer electrons
  4. All ions have the same size because they are isoelectronic

Q4. 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

Q5. 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

Q6. 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.

Q7. 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.

Q8. 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

Q9. 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

Q10. Which of the following best explains why elements in the same group of the Modern Periodic Table exhibit similar chemical properties?

  1. They have the same number of electron shells.
  2. They have the same number of valence electrons.
  3. They have similar atomic masses.
  4. They have identical atomic numbers.

Q11. Consider two elements, X and Y, where X has a smaller atomic radius but lower ionization enthalpy than Y. Which factor could explain this anomaly?

  1. Higher electron shielding in X
  2. X has a half-filled or fully filled subshell
  3. Y has a higher effective nuclear charge
  4. X has more protons than Y

Q12. 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.

Q13. Explain why the ionic radius of an anion is generally larger than that of its parent atom.

  1. Addition of electrons increases electron-electron repulsion, expanding the electron cloud
  2. The nuclear charge increases, pulling electrons closer
  3. The number of protons decreases, reducing attraction
  4. The atom loses electrons, causing the radius to increase

Q14. How did the discovery of atomic number influence the arrangement of elements in the Modern Periodic Table?

  1. It allowed elements to be arranged by increasing atomic mass.
  2. It resolved anomalies in Mendeleev's periodic table by arranging elements by nuclear charge.
  3. It grouped elements based on their melting points.
  4. It led to the classification of elements by their isotopic masses.

Q15. 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
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