Question

The electronegativity of the following elements increases in the order (1) \(\mathrm{C}, \mathrm{N}, \mathrm{S} i, \mathrm{P}\) (2) \(\mathrm{N}, \mathrm{Si}, \mathrm{C}, \mathrm{P}\) (3) \(\mathrm{Si}, \mathrm{P}, \mathrm{C}, \mathrm{N}\) (4) \(\mathrm{P}, \mathrm{Si}, \mathrm{N}, \mathrm{C}\)

Short answer

Option (3) Si < P < C < N is the correct order of increasing electronegativity.

Step-by-step solution

Understanding Electronegativity

Electronegativity is a chemical property that describes the ability of an atom to attract electrons towards itself in a covalent bond. Generally, electronegativity increases across a period from left to right and decreases down a group in the periodic table.

Identify Group Positions

Identify the group positions of the elements given: C (carbon) and N (nitrogen) are in the same period. Si (silicon) and P (phosphorus) are also in the same period but a different one from C and N.

Comparing C and N

Since C and N are in the same period, electronegativity increases from left to right. Thus, N has greater electronegativity than C.

Comparing Si and P

Similarly, within their respective period, P is to the right of Si. Therefore, P has greater electronegativity than Si.

Compare Across Periods

Compare elements across different periods: typically, elements in the second period (C, N) have higher electronegativity than elements in the third period (Si, P).

Arrange in Order

Given the patterns, the arrangement from lowest to highest electronegativity is: Si < P < C < N. Therefore, option (3) \(\text{{Si, P, C, N}}\) is the correct sequence.

Key concepts

Periodic Trends

Periodic trends refer to specific patterns observed within the periodic table, demonstrating how different elemental properties change. For electronegativity, a clear pattern emerges: it tends to increase as you move from left to right across a period and decreases as you move down a group. This means that elements on the right side of the periodic table are generally more electronegative than those on the left. Additionally, elements situated higher up in a group have higher electronegativity than those below them. These trends help predict and understand how elements will interact in chemical reactions.
For example:

• Fluorine, the most electronegative element, is located on the upper right corner of the periodic table.
• Lithium, which has a comparatively low electronegativity, is found on the bottom left.

Covalent Bonds

In chemistry, covalent bonds form when two atoms share one or more pairs of electrons. The strength and nature of a covalent bond depend significantly on the electronegativity of the atoms involved. Electronegativity differences determine how equally the electrons are shared in the bond.
If the difference in electronegativity between the two atoms is significant, the bond becomes polar covalent, meaning electrons are not shared equally. For instance:

• In a water molecule (H₂O), oxygen is more electronegative than hydrogen, creating a polar bond where electrons spend more time closer to the oxygen.

However, if the electronegativity difference is minimal, the bond remains nonpolar, and electrons are shared equally, such as in a nitrogen gas molecule (N₂), where both atoms have the same electronegativity.

Chemical Properties

Chemical properties describe a substance’s potential to undergo specific chemical changes. Electronegativity plays a crucial role in determining these properties because it influences how atoms form bonds and interact in chemical reactions. Elements with high electronegativity, such as oxygen and fluorine, often act as oxidizing agents since they tend to attract electrons.
Here are key points:

• Electronegativity can predict the type of bonding (ionic, covalent) that will occur between elements.
• It also helps in determining molecular polarity and reactivity.

Understanding the electronegativity of elements aids in anticipating the behavior of complex molecules in various chemical processes.

Periodic Table

The periodic table is a tabular arrangement of chemical elements based on their atomic number, electron configuration, and recurring chemical properties. It was developed by Dmitri Mendeleev in 1869 and has become an indispensable tool in chemistry.
Here are some critical aspects:

• Elements in the same group (vertical columns) have similar chemical properties, including trends in electronegativity.
• Periods (horizontal rows) show a progressive change in properties, including increasing electronegativity from left to right.

The periodic table not only helps predict the properties of elements but also facilitates an understanding of their relationships and behaviors in different chemical contexts. This makes it easier for students and chemists alike to analyze and synthesize new compounds efficiently.