Question

Explain the relationship between atomic size and reducing strength in Group \(1 \mathrm{~A}(1)\). Explain the relationship between IE and oxidizing strength in Group \(7 \mathrm{~A}(17)\)

Short answer

In Group 1A, atomic size increases down the group, enhancing reducing strength. In Group 7A, ionization energy decreases down the group, reducing oxidizing strength.

Step-by-step solution

- Understanding Atomic Size in Group 1A Elements

Atomic size, or atomic radius, increases as we move down Group 1A (alkali metals). This is because with each successive element, a new electron shell is added, making the atom larger.

- Relationship Between Atomic Size and Reducing Strength in Group 1A

As atomic size increases, the outermost electron is further from the nucleus and more shielded by inner electron shells. This makes it easier for the atom to lose this outer electron, enhancing its reducing strength. Thus, reducing strength increases as we move down Group 1A.

- Understanding Ionization Energy in Group 7A Elements

Ionization energy (IE) is the energy required to remove an electron from an atom. In Group 7A (halogens), ionization energy decreases as we move down the group because the outer electrons are further from the nucleus and more shielded by inner shells.

- Relationship Between Ionization Energy and Oxidizing Strength in Group 7A

Oxidizing strength refers to an element's ability to gain electrons. In Group 7A, higher ionization energy typically correlates with a stronger attraction for electrons (higher electronegativity). Therefore, elements at the top of Group 7A, with higher ionization energies, have stronger oxidizing strengths. This means oxidizing strength decreases as we move down Group 7A.

Key concepts

Group 1A (alkali metals)

Group 1A, also known as the alkali metals, includes elements such as lithium (Li), sodium (Na), and potassium (K). These elements are highly reactive, especially with water. Alkali metals have one electron in their outermost shell, which they tend to lose easily to form positive ions. As we move down the group from lithium to cesium, the reactivity of these metals increases due to the changes in atomic structure.

Atomic Radius

The atomic radius is the distance from the nucleus to the outermost electron. In Group 1A, the atomic radius increases as we move down the group. This happens because new electron shells are added with each successive element. For example:

• Lithium has an atomic radius of about 152 pm (picometers).
• Sodium’s atomic radius is roughly 186 pm.

The increase in radius makes the atoms larger and affects their chemical behavior.

Reducing Strength

Reducing strength refers to the ability of an element to lose electrons. In Group 1A, reducing strength increases as we move down the group. This is due to the larger atomic radius and the increased distance of the outermost electron from the nucleus. These factors make it easier for the atom to lose its outer electron. For instance:

• Cesium (Cs) has a strong reducing strength compared to lithium (Li).

This means cesium readily loses its outer electron, making it a more potent reducing agent.

Group 7A (halogens)

Group 7A, the halogens, include elements such as fluorine (F), chlorine (Cl), and bromine (Br). These elements are known for their high reactivity, particularly in forming salts with metals. Halogens have seven electrons in their outermost shell, needing just one more to achieve a stable octet configuration. As a result, they are very effective at gaining electrons in chemical reactions.

Ionization Energy

Ionization energy (IE) is the energy required to remove an electron from an atom. In Group 7A, ionization energy decreases as we move down the group. This is because the outer electrons are further from the nucleus and more shielded by inner electron shells, making them easier to remove. For example:

• Fluorine has a high ionization energy compared to iodine.

The decrease in ionization energy correlates with the elements' varying abilities to interact with other atoms.

Oxidizing Strength

Oxidizing strength refers to an element’s ability to gain electrons. In Group 7A, the oxidizing strength decreases as you move down the group. This is tied to ionization energy; elements with higher ionization energies at the top of the group, like fluorine, are stronger oxidizers. They have a greater tendency to attract and gain electrons. For example:

• Fluorine is a stronger oxidizer compared to chlorine and bromine.

This trend is a key factor in the chemical behavior of halogens in various reactions.