Question

Identify the correct order in which the covalent radius of the following elements increases: (1) \(\mathrm{Ti}\) \(\begin{array}{ll}\text { (2) } \mathrm{Ca} & \text { (3) } \mathrm{Sc}\end{array}\) (a) \((1),(2),(3)\) (b) \((2),(1),(3)\) (c) \((1),(3),(2)\) (d) \((3),(2),(1)\)

Short answer

Correct order is option (c): Ti, Sc, Ca.

Step-by-step solution

Understand Covalent Radius

The covalent radius is the measure of the size of an atom that forms part of a single covalent bond. Generally, the covalent radius increases down a group in the Periodic Table and decreases across a period from left to right.

Identify Element Positions

Identify the positions of Titanium (Ti), Calcium (Ca), and Scandium (Sc) on the Periodic Table. Titanium (Ti) is in Group 4, Calcium (Ca) is in Group 2, and Scandium (Sc) is in Group 3.

Determine Trends Within the Period

For elements in the same period (like Ti, Ca, and Sc which are in Period 4), the covalent radius tends to decrease as you move from left to right across the period. Thus, the covalent radius order will follow the trend increasing as you go from Ti to Sc to Ca.

Compare Covalent Radii

Using periodic trends, compare the covalent radii of Ti, Ca, and Sc. Since Ca is to the leftmost in Period 4 (Group 2) compared to Sc (Group 3) and Ti (Group 4), Ca will typically have the largest radius, followed by Sc, then Ti.

Select the Correct Order

The correct order for increasing covalent radii is: Titanium (Ti) < Scandium (Sc) < Calcium (Ca). This matches option (c) (1), (3), (2).

Key concepts

Periodic Table

The Periodic Table is a remarkable tool in the world of chemistry, serving as a complete list of chemical elements organized in a way that denotes recurring properties. Each element is placed in a specific location called a "position" based on atomic structure and properties. These positions are determined primarily by the number of protons in an element's nucleus.

• Elements are grouped into rows called periods (horizontal) which indicate an increasing number of proton shells.
• Vertical columns are called groups, and elements within a group exhibit similar chemical behavior.

Each element's properties are intricately linked to its location on the Periodic Table, including trends related to covalent radius. By understanding how elements are aligned, we can predict their behavior in chemical reactions and their physical characteristics.

Atomic Size

Atomic size, often discussed as the atomic or covalent radius, describes the size of an atom. The atomic radius is defined as half the distance between the nuclei of two atoms bonded together. Knowing the atomic size is essential because it helps in predicting and understanding atom interactions.

• Larger atomic sizes indicate atoms that are more spread out and have greater electron cloud sizes.
• As a general rule, the atomic size decreases across a period from left to right.

This happens because, within a period, the addition of more protons causes electrons to pull in closer to the nucleus, shrinking atom size. However, when moving down a group, the atomic size increases due to the addition of electron shells. Recognizing these trends aids in assessing atomic behavior within different environments.

Group Trends

Group trends in the Periodic Table refer to how certain properties of elements change as you move down a specific column or group. Understanding these trends is vital for predicting element behavior during reactions and interactions.

• The covalent radius increases as you move down a group. This is because each step down adds a new electron shell, pushing the outer electrons further away from the nucleus.
• Electronegativity usually decreases down a group as the increased distance weakens the nucleus's attractive force on electrons.

In a single period, like with Titanium, Calcium, and Scandium, these trends show a decrease in covalent radius from left to right. In any chemical study, leveraging these patterns can clarify how elements might bond or interact in a given state. Recognizing both intra-group and cross-period trends allows chemists to anticipate how an element might behave in a new or changing environment.