Question

1) Which ion does not have a noble gas configuration in its ground state? A) Sc3+ B) Al3+ C) Ga3+ D) As3-

2) Give the ground state electron configuration for Pb

3) Which of the following statements is false?

A) An orbital can accommodate at most two electrons.

B) The electron density at a point is proportional to ψ² at that point.

C) The spin quantum number of an electron must be either + 1/2 or – 1/2 .

D) A 2p orbital is more penetrating than a 2s; i.e., it has a higher electron density near the nucleus and inside the charge cloud of a 1s orbital.

E) In the usual order of filling, the 6s orbital is filled before the 4f orbital.

Answer 1

Question 1.

A) Sc3+ = [Ar] 3d1 4s2; when losing 3 electrons, [Ar]

B) Al3+ = [Ne] 3s2 3p1 when losing 3; then [Ne]

C) Ga3+ = [Ar] 3d10 4s2 4p1; when losing 3 = [Ar] 3d10

D) As3- = [Ar] 3d10 4s2 4p3; when gaining 3 electrons = [Ar] 3d10 4s2 4p6

which is the configuration for; Kr;  [Ar] 3d¹⁰ 4s² 4p⁶

Therefore, the best answer was gallium

C) Ga3+ = [Ar] 3d10 4s2 4p1; when losing 3 = [Ar] 3d10

Question 2.

For Pb

no of electrons = 82

Nearest config is that of Xenon;

Xenon has = 54 electrons

so we mustr account for 82-54 = 28 electrons

First, fill up the 4f; 14 electrons

then follow with 6s; 6p2 and finally 5d10

[Xe] 4f14 5d10 6s2 6p2

if you need all config, then add all Xe:

1s2 2s2 2p63s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6

Question 3.

A) An orbital can accommodate at most two electrons.

True, orbitals can accomodate depending on which one they are, but each individual can have either spin +1/2 or -1/2

i.e. s = 2; p = 6; but it is actually px = 2; py = 2. pz = 2

therefore, this is true

B) The electron density at a point is proportional to ψ2 at that point.

the value of y2 is proportional to the probability of fnidn an electron at tha tgiven point in space; therefore, this is true, since the electron density is a probability

C) The spin quantum number of an electron must be either + 1/2 or – 1/2 .

True, since ms is the spin uantum number and must be either +1/2 or -1/2

D) A 2p orbital is more penetrating than a 2s; i.e., it has a higher electron density near the nucleus and inside the charge cloud of a 1s orbital. False, 2s has much more penetration than a 2p due to its location

E) In the usual order of filling, the 6s orbital is filled before the 4f orbital.

True, the order goes as:

6 s < 4f < 5d < 6p < 7s < 5f < 6d