The correct answer is (C) Na, Be, C, Br.​

Pauling electronegativity measures an atom’s ability to attract electrons in a bond, with values increasing across periods and decreasing down groups in the periodic table. For these elements, Na (0.93 or 0.9) has the lowest value as a Group 1 metal, followed by Be (1.57) in Group 2, C (2.55) in Group 14, and Br (2.96) highest as a halogen in Group 17.​

Option Analysis

• (A) Be, Na, C, Br: Incorrect, as Na (0.93) is lower than Be (1.57).​

• (B) Br, C, Na, Be: Incorrect, as this shows decreasing order instead of increasing.​

• (C) Na, Be, C, Br: Correct, matching the values Na < Be < C < Br.​

• (D) Na, C, Be, Br: Incorrect, as C (2.55) precedes Be (1.57).​

The electronegativity order Na Be C Br Pauling scale follows Na (0.93) < Be (1.57) < C (2.55) < Br (2.96), key for understanding bond polarity in CSIR NET chemistry questions. This trend reflects periodic table patterns where metals like Na and Be show low values, nonmetals like C moderate, and halogens like Br high.​

Pauling developed this scale in 1932 using bond energy differences, assigning F the highest value (4.0). Values help predict covalent, ionic, or polar bonds—low differences mean nonpolar, high mean ionic.​

Periodic Trends Explained

Electronegativity rises left-to-right across periods due to increasing nuclear charge and shrinks down groups from larger atomic size.​

• Na (Period 3, Group 1): Lowest, loses electrons easily.​

• Be (Period 2, Group 2): Higher than Na, smaller size.​

• C (Period 2, Group 14): Moderate, forms strong covalent bonds.​

• Br (Period 4, Group 17): High, attracts electrons strongly.​

CSIR NET Practice Tips

For exams like CSIR NET Life Sciences, memorize key values and trends to solve quickly. Practice with similar MCQs on alkali metals vs halogens.​