Question

which of the following represent the proper long hand form electron configuration of zirconium, zr, using the building - up principle?
kr 5s² 4d²
kr 4d² 5s²
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 5s² 4d²
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d² 5s²
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d²

question 4
1 pts
which of the following represent the proper short hand form electron configuration of yttrium, y, using the building - up principle?
kr 5s² 4d¹
xe 5s² 4d¹
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹ 5s²
kr 4d¹ 5s²

Explanation:

Step1: Recall electron - filling order

Electrons fill orbitals in the order 1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d etc. according to the building - up principle.

Step2: Determine atomic number of zirconium (Zr)

Zirconium has an atomic number of 40. The noble - gas core before Zr is Kr (atomic number 36). So, we need to account for 40 - 36=4 more electrons. These electrons fill the 5s and 4d orbitals. The 5s orbital fills before the 4d orbital and can hold 2 electrons, and then the 4d orbital holds the remaining 2 electrons. The long - hand electron configuration of Zr is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}5s^{2}4d^{2}$.

Step3: Determine atomic number of yttrium (Y)

Yttrium has an atomic number of 39. The noble - gas core before Y is Kr (atomic number 36). We need to account for 39 - 36 = 3 more electrons. The 5s orbital fills first and can hold 2 electrons, and then the 4d orbital holds 1 electron. The short - hand electron configuration of Y is $[Kr]5s^{2}4d^{1}$.

Answer:

Question 1: $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}5s^{2}4d^{2}$
Question 2: $[Kr]5s^{2}4d^{1}$