Question

State where in the periodic table these elements appear: (a) elements with the valence-shell electron configuration \(n s^{2} n p^{5}\) (b) elements that have three unpaired \(p\) electrons (c) an element whose valence electrons are \(4 s^{2} 4 p^{1}\) (d) the \(d\) -block elements

Short answer

(a) Elements with the valence-shell electron configuration \(n s^{2} n p^{5}\) are located in Group 17, known as halogens. (b) Elements with three unpaired p electrons (\(np^{3}\)) are located in Group 15, known as the nitrogen group or pnictogens. (c) An element with valence electrons \(4s^{2} 4p^{1}\) is Gallium (Ga), which is in Period 4 and Group 13. (d) The d-block elements are located in the center of the periodic table and comprise Groups 3 through 12, including Transition Metals.

Step-by-step solution

(a) Valence-shell electron configuration of \(n s^{2}np^{5}\) elements

To locate elements with this valence-shell electron configuration, remember that elements in the periodic table are arranged in periods and groups. A period is denoted by the principal quantum number n, and groups represent elements that have similar electron configurations. Elements with the electron configuration \(ns^{2}np^{5}\) belong to Group 17, known as halogens.

(b) Elements with three unpaired p electrons

Having three unpaired p electrons means that the element's electron configuration in the p orbital is \(np^{3}\). These elements are located in Group 15 of the periodic table, known as the nitrogen group or pnictogens.

(c) Valence electrons are \(4s^{2} 4p^{1}\)

To determine the element with these valence electrons, consider both the period and the group it belongs to. Here, the principal quantum number n is 4, indicating that the element is in Period 4. Also, its electron configuration indicates that it belongs to Group 13. Consequently, the element is Gallium (Ga).

(d) The d-block elements

The d-block elements are located in the center of the periodic table and comprise Groups 3 through 12, including Transition Metals. In these elements, d orbitals are progressively filled from left to right across the block.

Key concepts

Valence-shell electron configuration

The valence-shell electron configuration describes the distribution of electrons in the outermost shell of an atom. Electrons occupy orbitals in a systematic way, starting from the lowest energy level and moving to higher levels. Valence electrons are crucial as they determine the chemical properties and reactivity of an element.

Consider the configuration of the halogens, which is expressed as \(ns^{2}np^{5}\). Breaking it down, \(n\) stands for the principal quantum number, indicating the period, \(s\) indicates the \(s\)-orbital with 2 electrons, and \(p^{5}\) signifies that 5 electrons are present in the \(p\)-orbitals. This configuration shows that halogens are highly reactive as they seek one more electron to achieve a stable noble gas configuration. The valence-shell electron configuration provides a key understanding of an element’s position on the periodic table.

Group 17 Halogens

Group 17 in the periodic table is known as the Halogens. This includes elements like fluorine, chlorine, bromine, iodine, and astatine. These nonmetals are located in the penultimate column of the periodic table and have a valence-shell configuration of \(ns^{2}np^{5}\).

• These elements are known for their high reactivity, especially with alkali metals and alkaline earth metals, with which they form salts.
• Halogens are found in different states under normal conditions. For example, fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids.
• Their ability to readily gain an electron makes them excellent oxidizing agents.

The reactivity and physical states of halogens showcase the incredible diversity within a single group of elements on the periodic table.

Group 15 Pnictogens

The Pnictogens occupy Group 15 in the periodic table. This group includes nitrogen, phosphorus, arsenic, antimony, and bismuth, with a characteristic valence-shell electron configuration of \(ns^{2}np^{3}\).

In this configuration, we have three unpaired \(p\) electrons, which influence the chemical behavior of these elements. Pnictogens possess:

• Diverse oxidation states, allowing them to form various compounds ranging from binary oxides to complex organometallics.
• Varied physical properties, with nitrogen as a colorless gas, phosphorus in multiple allotropes, and bismuth as a dense metal.
• A significant role in biological systems, especially nitrogen and phosphorus, which are essential for nucleic acids and ATP.

Their unique electronic properties make them invaluable both in industrial applications and biological systems.

d-block Transition Metals

The d-block of the periodic table contains the transition metals, found in Groups 3 through 12. Their defining feature is the filling of \(d\) orbitals, which are typically partially filled in their common oxidation states.

• These metals include familiar elements such as iron, copper, and gold.
• Transition metals are known for their ability to form complex ions with varied oxidation states, which lends them a variety of colors.
• They are also characterized by their excellent conductivity and strength, making them indispensable in construction and electronics.
• Moreover, due to their d orbitals, these elements are heavily involved in catalytic activities, crucial for many chemical reactions and industrial processes.

The defining characteristics of the d-block transition metals underline their critical importance in technology and manufacturing, as well as their diverse chemical functionalities.