Question

State where in the periodic table these elements appear: $$ \begin{array}{l}{\text { (a) elements with the valence-shell electron configuration }} \\ {n s^{2} n p^{5}} \\ {\text { (b) elements that have three unpaired p electrons }} \\ {\text { (c) an element whose valence electrons are } 4 s^{2} 4 p^{1}} \\ {\text { (d) the } d \text { -block elements [ Section } 6.9 ]}\end{array} $$

Short answer

In short, the elements with the given configurations or properties can be found in the following groups on the periodic table: 1. Elements with the electron configuration \(ns^2 np^5\) - Group 17 (Halogens). 2. Elements with three unpaired p-electrons (\(ns^2 np^3\)) - Group 15 (Nitrogen group or Pnictogens). 3. An element with valence electrons of configuration \(4s^2 4p^1\) - Group 13 (Gallium). 4. The d-block elements - Groups 3 to 12 (Transition metals).

Step-by-step solution

(Step 1: Locating elements with \(ns^2 np^5\) electron configuration)

Elements with the electron configuration \(ns^2 np^5\) are located in Group 17 of the periodic table. These elements are called halogens, and examples include Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).

(Step 2: Locating elements with three unpaired p-electrons)

Elements with three unpaired p-electrons have the electron configuration of \(ns^2 np^3\), where there are three electrons in the p-subshell. These elements are located in Group 15 of the periodic table, also known as the Nitrogen group or pnictogens. Examples include Nitrogen (N), Phosphorus (P), Arsenic (As), Antimony (Sb), and Bismuth (Bi).

(Step 3: Locating an element with valence electrons of \(4s^2 4p^1\) electron configuration)

To identify an element with valence electrons having the configuration \(4s^2 4p^1\), first, note that the sum of the electrons in the given configuration is 3 (i.e., 2 electrons in the s-subshell and 1 electron in the p-subshell). The element with a total of 3 electrons in the 4th period is Gallium (Ga). It is located in Group 13 of the periodic table.

(Step 4: Locating the d-block elements)

The d-block elements are found in the central portion of the periodic table, which comprises Groups 3 to 12. These elements are inhabited by the transition metals, such as scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn), among others. In these elements, d-orbitals are being filled with electrons.

Key concepts

Valence-Shell Electron Configuration

Understanding the valence-shell electron configuration is crucial in determining an element's chemical behavior and its placement in the periodic table. The valence shell is the outermost shell of an atom that is involved in chemical bonding. The electrons in this shell are called valence electrons, and the configuration refers to the arrangement of these electrons.

Take, for instance, the configuration noted in the exercise as ns² np⁵. Here, 'n' represents the quantum number indicative of the energy level or shell, 's' and 'p' refer to the type of subshell, and the superscripts indicate the number of electrons in those subshells. The Group 17 elements, which follow this pattern, are highly reactive nonmetals known as halogens. They seek one additional electron to achieve a filled-shell configuration, which makes them powerful oxidizing agents.

Such configurations help predict the reactive nature and the types of bonds an element might form. Moreover, mastering electron configurations enables us to understand the entire landscape of the periodic table, from the alkali metals of Group 1 to the noble gases of Group 18, and every family in between.

Group Identification in Periodic Table

The periodic table organizes elements according to their atomic structure and properties. Group identification is a method of categorizing elements based on their valence-shell electron configuration. Groups, also known as families, are vertical columns in the periodic table and share common chemical characteristics. For example, elements with the configuration ns² np³ belong to Group 15. These elements have three unpaired p-electrons, like those of nitrogen (N) and phosphorus (P), and this configuration results in certain similarities in their chemical behavior.

Determining an element's group aids in predicting reactions and bonding patterns. It also simplifies the study of chemical trends across periods (horizontal rows) and down groups, such as ionization energies, electronegativity, and atomic radii. Recognizing group patterns is vital for anyone venturing into chemistry, whether it's for solving simple exercises or engaging in complex research projects.

d-block Elements

The d-block elements, commonly known as transition metals, are a bridge between the extremely reactive metals on the left side of the periodic table and the nonmetals on the right side. They are located in Groups 3 through 12 and are characterized by the gradual filling of their d-orbitals with electrons. These elements exhibit properties that are typical of metals – such as luster, high density, and high melting points – and they often form colored compounds, which makes them easy to identify in the laboratory.

A quintessential feature of d-block elements is their ability to form various oxidation states, which is a direct consequence of the energetics of their electron configuration. This gives rise to their involvement in a plethora of chemical reactions, making them essential in fields such as catalysis and materials science. For example, iron (Fe), a d-block element, can exist in multiple oxidation states, which is why it's a key component in the function of hemoglobin in blood.

p-block Elements

The p-block elements occupy the right side of the periodic table, starting from Group 13 to Group 18. These elements have their valence electrons filling up the p-orbitals. Their electron configurations can be expressed as ns² np^1-6, with the 'n' indicating the period and '1-6' the varying number of electrons in the p-orbitals.

The p-block encompasses a diverse range of elements, including metals, nonmetals, and metalloids, thus showing a wide variety of properties. For example, carbon (C), a Group 14 element, has an electron configuration of 2s² 2p² and is fundamental to all known life, while oxygen (O), with an electron configuration of 2s² 2p⁴ in Group 16, is essential for respiration.

Their capacity to form diverse types of compounds, from simple diatomic molecules to large polymers, makes p-block elements crucial in both organic and inorganic chemistry. Their chemistry is governed by the trends in electronegativity and electron affinity, alongside the octet rule—where atoms tend to gain, lose, or share electrons to achieve eight in their valence shell—a guideline of stability for many elements in this block.