Question

Identify each element below, and give the symbols of the other elements in its group: (a) \([\mathrm{He}] 2 s^{2} 2 p^{1}\) (b) \([\mathrm{Ne}] 3 s^{2} 3 p^{4}\) (c) \([\mathrm{Xe}] 6 s^{2} 5 d^{1}\)

Short answer

(a) B (Group 13: B, Al, Ga, In, Tl); (b) S (Group 16: O, S, Se, Te, Po); (c) La (Lanthanides: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)

Step-by-step solution

Identify the Element (a)

Using the electron configuration \([\text{He}] 2s^{2} 2p^{1}\), identify the element. The configuration corresponds to atomic number 5, which is Boron (B).

Identify the Group for Element (a)

Boron (B) is in Group 13 of the periodic table. The elements in Group 13 are B, Al, Ga, In, and Tl.

Identify the Element (b)

Using the electron configuration \([\text{Ne}] 3s^{2} 3p^{4}\), identify the element. The configuration corresponds to atomic number 16, which is Sulfur (S).

Identify the Group for Element (b)

Sulfur (S) is in Group 16 of the periodic table. The elements in Group 16 are O, S, Se, Te, and Po.

Identify the Element (c)

Using the electron configuration \([\text{Xe}] 6s^{2} 5d^{1}\), identify the element. The configuration corresponds to atomic number 57, which is Lanthanum (La).

Identify the Group for Element (c)

Lanthanum (La) is part of the Lanthanides series. The elements in the Lanthanides are La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

Key concepts

Periodic Table Groups

The periodic table groups are essential for understanding the properties and behavior of elements.
Groups, also known as families, are the vertical columns in the periodic table. Each group contains elements with similar chemical properties.
Elements in the same group often have the same number of valence electrons, which determines how they interact in chemical reactions.
For example, Group 1 (the alkali metals) all have one valence electron and are highly reactive.
In our exercise, Boron (B) is in Group 13, characterized by having three valence electrons. Group 13 includes Boron (B), Aluminium (Al), Gallium (Ga), Indium (In), and Thallium (Tl).
Understanding these groupings can help predict the behavior of unknown elements, simply by their placement in the periodic table.

Atomic Number

Each element has a unique atomic number, which is the number of protons in its nucleus.
This number determines the element's identity and its position on the periodic table.
In the provided exercise, for example, the electron configuration \([\text{He}] 2s^2 2p^1\) corresponds to an atomic number of 5.
By looking up atomic number 5 on the periodic table, you can identify the element as Boron (B).
Similarly, the configuration \([\text{Ne}] 3s^2 3p^4\) corresponds to atomic number 16, Sulfur (S), and the configuration \([\text{Xe}] 6s^2 5d^1\) corresponds to atomic number 57, Lanthanum (La).
Recognizing the atomic number’s role helps in identifying elements and predicting their chemical properties.

Lanthanides

The Lanthanides series includes 15 elements, spanning from Lanthanum (La) to Lutetium (Lu).
These elements are found in the f-block of the periodic table and are often grouped separately at the bottom.
Lanthanides are known for having similar chemical properties, such as being silvery-white metals and often exhibiting +3 oxidation states.
They are used in various high-tech applications, from catalysts to phosphors in light-emitting diodes (LEDs).
In our exercise, Lanthanum (La) was identified with the electron configuration \([\text{Xe}] 6s^2 5d^1\).
Knowing the properties of the Lanthanides can be particularly useful in fields like material science and chemistry.