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 $4s^{2}4p^1$ (d) the $d$-block elements [Section 6.9]

Short answer

(a) Elements with valence-shell electron configuration $n{s}^{2}n{p}^5$ are in Group 17 (halogens), e.g., Fluorine (F), Chlorine (Cl), Bromine (Br). (b) Elements with three unpaired p electrons are in Group 15 (Nitrogen group or Pnictogens), e.g., Nitrogen (N), Phosphorus (P), Arsenic (As). (c) The element with valence electrons $4s^{2}4p^1$ is in Group 13 and the 4th period, which corresponds to Gallium (Ga). (d) The d-block elements are in Groups 3-12 and are known as transition metals, e.g., Scandium (Sc), Iron (Fe), and Gold (Au).

Step-by-step solution

(a) Find elements with valence-shell electron configuration $n{s}^{2}n{p}^5$

To find these elements in the periodic table, we need to realize that a valence electron configuration of $n{s}^{2}n{p}^5$ indicates elements in Group 17 (group VIIA in old notation), which are the halogens. These elements are one electron short of a closed-shell electron configuration and thus are highly reactive. Examples of halogens are Fluorine (F), Chlorine (Cl), and Bromine (Br).

(b) Find elements with three unpaired p electrons

Elements that have three unpaired p electrons fall into Group 15 (group VA in old notation), which are known as the Nitrogen group or Pnictogens. The presence of three unpaired electrons in the p subshell allows these elements to form three covalent bonds with other atoms. Examples of Group 15 elements are Nitrogen (N), Phosphorus (P), and Arsenic (As).

(c) Identify element with valence electrons $4s^{2}4p^1$

An element with electron configuration having 4s² 4p¹ valence electrons indicates that it falls in the 4th period and 1st element of the p-block in the periodic table. This corresponds to Group 13 (group IIIA in old notation), which houses the element Gallium (Ga).

(d) Identify the d-block elements

The d-block elements are found in the center of the periodic table and are often referred to as transition metals. These elements have the outermost d orbital being progressively filled with electrons as one moves from left to right in the periodic table. The d-block elements span from Group 3 (group IIIB in old notation) to Group 12 (group IIB in old notation). Examples of d-block elements include Scandium (Sc), Iron (Fe), and Gold (Au).

Key concepts

Valence-Shell Electron Configuration

Understanding the valence-shell electron configuration of an element is like having a map to its chemical behavior. For example, the configuration $n{s}^{2}n{p}^5$ belongs to elements in Group 17 of the periodic table known as the halogens. This configuration is just one electron short of a stable noble gas configuration, $n{s}^{2}n{p}^6$, making these elements highly reactive.
Halogens like Fluorine (F), Chlorine (Cl), and Bromine (Br) aggressively seek an electron to complete their outer shell. This trait makes them excellent oxidizing agents, often reacting with metals to form salts.

• They have 7 electrons in their outermost shell.
• They are part of the p-block in the periodic table.
• This configuration leads to their high reactivity and tendency to form negative ions.

Halogens

Halogens are fascinating elements located in Group 17 (or VIIA) of the periodic table. They include Fluorine, Chlorine, Bromine, Iodine, and Astatine. Named from the Greek 'salt-producing,' halogens have several unique properties.
These elements exhibit high electronegativity and are excellent at forming halide ions by gaining one electron. Their diatomic molecules, such as ${\text{F}}_2$ and ${\text{Cl}}_2$, exist as gases under standard conditions, while others like iodine form solids.

• Highly reactive, especially with alkali metals and alkaline earth metals.
• They form salts, like sodium chloride, when reacting with metals.
• Are used in various applications such as disinfectants and Teflon manufacturing.

Transition Metals

Transition metals occupy the d-block groups of the periodic table, from Groups 3 to 12. These metals have partially filled d orbitals, which means they can exhibit multiple oxidation states. This property is key to their widespread use in catalysts and the colorfully rich compounds they form.
Some well-known transition metals include Iron (Fe), Copper (Cu), and Gold (Au). They often display properties such as ductility, high electrical and thermal conductivity, and are typically shiny and hard.

• They are often found in ores containing oxygen and sulfur.
• Capable of forming colored compounds due to d-d electron transitions.
• Play essential roles in biological processes, e.g., Iron in hemoglobin.

Pnictogens

The pnictogens are the elements in Group 15 of the periodic table, also known as the Nitrogen group. This group includes elements like Nitrogen (N), Phosphorus (P), and Arsenic (As).
The term 'pnictogen' is derived from the Greek word 'pnigein,' meaning suffocate, reflective of nitrogen's suffocating nature when present in large concentrations.

• These elements have five valence electrons: two s electrons and three p electrons.
• Their ability to form three covalent bonds allows for the creation of a variety of compounds.
• Nitrogen is crucial for living organisms as it is a component of amino acids and nucleic acids.