The metals of Group 2 from top to bottom are Be, Mg, Ca, Sr and Ba.
The metals of Group 2 from top to bottom are Be, Mg, Ca, Sr and Ba.
The correct option is D Ba
The correct answer is option D
Explanation of correct answer
Increasing the order of elements according to atomic size is Be ‹ Mg ‹ Ca ‹ Sr ‹ Ba
Group 2 elements are called alkaline earth metals. On moving down a group atomic size increases and the force of attraction between the nucleus and the valence electrons decrease. So a small amount of energy is required to remove the electrons from its valence shell. That is ionisation energy is less. Ionisation energy decreases down a group due to an increase in atomic size. So Barium forms ions more readily than other elements.
Explanation of incorrect answer
option (A) Be - Atomic number 4. Electronic configuration 2,2 . The first element in group 2. It has only 2 shells. Atomic size is very less.
option (B) Mg - Atomic number 12. Electronic configuration 2,8,2. The second element in group 2. There are 3 shells. It has a greater atomic size compared to Be
option (C) Ca - Atomic number 20. Electronic configuration 2,8,8, 2 . Third element in group 2. There are 4 shells. It has a greater atomic size compared to Ca
option (E) Sr - Atomic number 38. Electronic configuration 2,8, 18, 8, 2 . Fourth element in group 2.There are 5 shells. It has a greater atomic size compared to Sr
Conclusion
Barium has a greater atomic size and readily becomes ions
Ba
The correct answer is option D
Explanation of correct answer
Increasing the order of elements according to atomic size is Be ‹ Mg ‹ Ca ‹ Sr ‹ Ba
Group 2 elements are called alkaline earth metals. On moving down a group atomic size increases and the force of attraction between the nucleus and the valence electrons decrease. So a small amount of energy is required to remove the electrons from its valence shell. That is ionisation energy is less. Ionisation energy decreases down a group due to an increase in atomic size. So Barium forms ions more readily than other elements.
Explanation of incorrect answer
option (A) Be - Atomic number 4. Electronic configuration 2,2 . The first element in group 2. It has only 2 shells. Atomic size is very less.
option (B) Mg - Atomic number 12. Electronic configuration 2,8,2. The second element in group 2. There are 3 shells. It has a greater atomic size compared to Be
option (C) Ca - Atomic number 20. Electronic configuration 2,8,8, 2 . Third element in group 2. There are 4 shells. It has a greater atomic size compared to Ca
option (E) Sr - Atomic number 38. Electronic configuration 2,8, 18, 8, 2 . Fourth element in group 2.There are 5 shells. It has a greater atomic size compared to Sr
Conclusion
Barium has a greater atomic size and readily becomes ions
