Question

Discuss the trend of following properties for Group 14 elements. (a) Atomic Size (b) lonisation energy (c) Electronegativity (d) Metallic Character

Short answer

In Group 14 elements, atomic size increases, ionisation energy decreases, electronegativity decreases, and metallic character increases as you move from Carbon (C) to Lead (Pb) down the group.

Step-by-step solution

Discuss Atomic Size

The atomic size generally increases on moving down a group due to the addition of new energy levels, therefore, atomic size increases from Carbon (C) to Lead (Pb) in Group 14.

Discuss Ionisation Energy

Ionisation energy decreases on moving down a group because the outermost electrons get farther from the nucleus and thus, can be removed more readily. So, ionisation energy decreases from Carbon to Lead in Group 14.

Discuss Electronegativity

Electronegativity decreases as you go down a group. This is due to the larger radius, which decreases the attraction between the outermost electrons and the nucleus. Therefore, electronegativity decreases from Carbon to Lead in Group 14.

Discuss Metallic Character

Metallic character increases on moving down a group due to the increase in size and decrease in ionisation energy. Therefore, for Group 14, the metallic character increases from Carbon to Lead.

Key concepts

Atomic Size Trend

Understanding the atomic size trend within Group 14 elements is fundamental to grasping chemical periodicity. This trend showcases the relative sizes of atoms within the group, which encompass carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb).

As we journey down the group, each element gains an additional energy level, or shell, which increases the distance between the nucleus and the outermost electrons. This results in atoms that are progressively larger in size. For instance, lead, at the bottom of the group, has a significantly larger atomic radius than the compact carbon atom at the top.

Ionisation Energy Trend

Ionisation energy is another critical concept that reflects the energy required to remove an electron from an atom in the gaseous state. In Group 14, there is an observable trend where ionisation energy diminishes as we move from carbon towards lead.

The reasoning behind this lies in the increasing atomic size. As atoms get larger, their outermost electrons are less tightly bound to the nucleus due to the greater distance and interceding electron layers. This reduced attraction makes it easier to ionise these atoms, hence the decreased ionisation energy. This concept is crucial for predicting the reactivity of these elements.

Electronegativity Trend

Grasping the concept of electronegativity, which measures an atom's tendency to attract and hold onto electrons when it forms a chemical bond, is vital for understanding molecular interactions. Within Group 14, electronegativity diminishes from top to bottom.

The underlying cause of this trend is the increase in atomic size. As atoms grow in size, there's a concurrent increase in the distance between the nucleus and the valence electrons. This greater distance reduces the nucleus's pull on electrons shared in a chemical bond, resulting in lower electronegativity. Carbon, situated at the top of the group, is therefore the most electronegative, while lead is the least.

Metallic Character Trend

The metallic character of an element is indicative of its behavior and properties akin to metals, such as malleability, ductility, and electrical conductivity. In Group 14, the metallic character ascends from carbon to lead.

This enhancement in metallic traits is attributable to the reduction of ionisation energy coupled with the hike in atomic size. With less energy required to lose electrons, the lower group elements more readily exhibit metallic characteristics. Elements like carbon exhibit nonmetallic properties, whereas lead, further down the group, shows pronounced metallic behavior. This diversity within the group yields broad applications, from semiconductor technology to lead-acid batteries.