Electronic Structure (Ps 25)

1. Which electron configuration corresponds to that of a noble gas?

The electron configuration of a noble gas corresponds to a completely filled outer electron shell. This means that the outermost energy level of the atom is filled with the maximum number of electrons it can hold. Noble gases are known for their stability and lack of reactivity due to this electron configuration. Therefore, the correct answer would be the electron configuration that represents a completely filled outer shell.

Explanation

The electron configuration of a noble gas corresponds to a completely filled outer electron shell. This means that the outermost energy level of the atom is filled with the maximum number of electrons it can hold. Noble gases are known for their stability and lack of reactivity due to this electron configuration. Therefore, the correct answer would be the electron configuration that represents a completely filled outer shell.

2. Which element has a valence electron configuration of ?

Li

Na

K

Rb

Cs

The element with a valence electron configuration of [Ar] 4s1 is K (potassium). This means that potassium has one valence electron in its outermost energy level.

Explanation

The element with a valence electron configuration of [Ar] 4s1 is K (potassium). This means that potassium has one valence electron in its outermost energy level.

3. Which of the following elements has the greatest number of p electrons?

C

Si

Fe

Cl

As

As (arsenic) has the greatest number of p electrons among the given elements. The electron configuration of As is [Ar] 3d10 4s2 4p3, which means it has 5 p electrons. In comparison, C (carbon) has 2 p electrons, Si (silicon) has 3 p electrons, Fe (iron) has 0 p electrons, and Cl (chlorine) has 3 p electrons. Therefore, As has the greatest number of p electrons.

Explanation

As (arsenic) has the greatest number of p electrons among the given elements. The electron configuration of As is [Ar] 3d10 4s2 4p3, which means it has 5 p electrons. In comparison, C (carbon) has 2 p electrons, Si (silicon) has 3 p electrons, Fe (iron) has 0 p electrons, and Cl (chlorine) has 3 p electrons. Therefore, As has the greatest number of p electrons.

4. Which of the following is an impossible set of quantum numbers?

2, 0, 0, 1/2

2, 1, -1, -1/2

3, 1, -1, +1/2

1, 1, 1, -1/2

3, 2, 1, 1/2

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Explanation

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5. Which of the following elements has an electron configuration that does NOT follow the Aufbau principle?

Fe

Mg

Al

Ag

Ni

Ag (Silver) has an electron configuration that does NOT follow the Aufbau principle. The Aufbau principle states that electrons fill the lowest energy levels first before moving to higher energy levels. However, in the case of Ag, the electron configuration is [Kr] 4d^10 5s^1, which suggests that one electron from the 4d orbital has moved to the 5s orbital. This violates the Aufbau principle as the 4d orbital should be filled before moving to the 5s orbital.

Explanation

Ag (Silver) has an electron configuration that does NOT follow the Aufbau principle. The Aufbau principle states that electrons fill the lowest energy levels first before moving to higher energy levels. However, in the case of Ag, the electron configuration is [Kr] 4d^10 5s^1, which suggests that one electron from the 4d orbital has moved to the 5s orbital. This violates the Aufbau principle as the 4d orbital should be filled before moving to the 5s orbital.