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4.2: Introduction to Atoms and Elements

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    Identify the building blocks of matter

    At its most fundamental level, life is made up of matter. Matter is any substance that occupies space and has mass. Elements are unique forms of matter with specific chemical and physical properties that cannot be broken down into smaller substances by ordinary chemical reactions. There are 118 elements, but only 92 occur naturally. The remaining elements are synthesized in laboratories and are unstable.

    Each element is designated by its chemical symbol, which is a single capital letter or, when the first letter is already “taken” by another element, a combination of two letters. Some elements follow the English term for the element, such as C for carbon and Ca for calcium. Other elements’ chemical symbols derive from their Latin names; for example, the symbol for sodium is Na, referring to natrium, the Latin word for sodium.

    The four elements common to all living organisms are oxygen (O), carbon (C), hydrogen (H), and nitrogen (N). In the non-living world, elements are found in different proportions, and some elements common to living organisms are relatively rare on the earth as a whole, as shown in Table 1. For example, the atmosphere is rich in nitrogen and oxygen but contains little carbon and hydrogen, while the earth’s crust, although it contains oxygen and a small amount of hydrogen, has little nitrogen and carbon. In spite of their differences in abundance, all elements and the chemical reactions between them obey the same chemical and physical laws regardless of whether they are a part of the living or non-living world.

    Table 1. Approximate Percentage of Elements in Living Organisms (Humans) Compared to the Non-living World
    Element Life (Humans) Atmosphere Earth’s Crust
    Oxygen (O) 65% 21% 46%
    Carbon (C) 18% trace trace
    Hydrogen (H) 10% trace 0.1%
    Nitrogen (N) 3% 78% trace

    What You’ll Learn to Do

    • Draw a diagram of an atom, according to current scientific understanding
    • Understand the periodic table of elements and how to use it to understand elements
    • Describe the behavior and location of electrons, and how these factors influence bond formation between atoms

    Learning Activities

    The learning activities for this section include the following:

    • Atoms
    • The Periodic Table of Elements
    • Electrons
    • Self Check: Atoms and Elements

    Contributors and Attributions

    CC licensed content, Original
    • Introduction to Atoms and Elements. Authored by: Shelli Carter and Lumen Learning. Provided by: Lumen Learning. License: CC BY: Attribution
    CC licensed content, Shared previously

    4.2: Introduction to Atoms and Elements is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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