The subatomic particles responsible for the chemical behavior of atoms are
(a) Electrons
(b) Ions
(c) Neutrons
(d) Protons

Verified step by step guidance

1. Step 1: Understand the question is asking to identify which element is NOT one of the four major elements that contribute most to the human body's mass.
2. Step 2: Recall that the four major elements making up the majority of body mass are Oxygen (O), Carbon (C), Hydrogen (H), and Nitrogen (N). These elements are fundamental components of organic molecules and water in the body.
3. Step 3: Review the options given: Hydrogen, Carbon, Nitrogen, Sodium, and Oxygen.
4. Step 4: Compare each option to the list of major elements. Hydrogen, Carbon, Nitrogen, and Oxygen are all part of the four major elements.
5. Step 5: Identify Sodium as the element that does not belong to the four major elements contributing to body mass, as it is a minor element important for other physiological functions but not a major mass contributor.

Key Concepts

Four Major Elements of Body Mass

The human body is primarily composed of four major elements: oxygen, carbon, hydrogen, and nitrogen. These elements make up the bulk of organic molecules such as proteins, lipids, carbohydrates, and nucleic acids, which are essential for life.

Role of Trace Elements

Trace elements like sodium, potassium, and calcium are present in smaller amounts but are vital for physiological functions such as nerve transmission and muscle contraction. However, they do not contribute significantly to overall body mass.

Elemental Composition and Body Mass

Body mass is largely determined by the abundance of major elements forming organic compounds. Elements not part of these major groups, even if biologically important, contribute minimally to total body mass.