Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
AP EAMCET202017 Sep 2020Morning ShiftChemistryClassification of Elements and Periodicity in PropertiesActual

Assertion (A) Boron has a smaller first ionisation enthalpy than beryllium. Reason (R) The penetration of a (2 s )-electron to the nucleus is more than the (2 p )-electron hence, (2 p )-electron is more shielded by the inner core of electrons than (2 ~s )-electrons.

Options

  1. AAssertion and Reason both are correct statements but Reason is not correct explanation for Assertion.
  2. BAssertion is correct statement but Reason is wrong statement.
  3. CAssertion and Reason both are correct statements and Reason is correct explanation for Assertion.
  4. DAssertion and Reason both are wrong statements.

Correct answer

C. Assertion and Reason both are correct statements and Reason is correct explanation for Assertion.

Step-by-step solution

Assertion (A) Electronic configuration of boron ((Z=5) ) is [He] (2 s^2 2 p^1 ). So, in first ionisation ( (1 IE ₁ ) or ( _i H₁ ) ) removal will take place from unpaired (p^1 )-electron. Whereas that of Be will be from paired (2 s^2 )-electrons which requires more energy. Electronic configuration of ( Be (Z=4):[ He ] 2 s^2 ) So, the Assertion is a correct statement. Reason (R) (s )-orbital is being symmetrical in shape (spherical), it shields nuclear force (nuclear charge) strongly. So, (2 p^1 )-electron of (B ) is

Practice Classification of Elements and Periodicity in Properties on Quantrex Academy →

More from Classification of Elements and Periodicity in Properties

Which of the following is an INCORRECT match? 2026Match List-I with List-II: List-I (Element-Atomic number) List-II (Position in periodic table) (a) Ra – 88 (i) 4^ th period, 13^ th group (b) Ga – 31 (ii) 6^ th period, 6^ th group 2026Which element from following has positive electron gain enthalpy? 2026Which of the following elements belongs to group 2 and sixth period of periodic table? 2026Identify the most electronegative element by the following. 2026Identify increasing order of acidity for following diprotic acids in aqueous solutions. 2026Identify the group of periodic table that contains element Astatine. 2026What happens to the size of atoms in p-block elements when we move from left to right in the same period? 2026 Full Classification of Elements and Periodicity in Properties list All AP EAMCET PYQs