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  2. Composition of the human body - Wikipedia

    en.wikipedia.org/wiki/Composition_of_the_human_body

    Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm. About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium ...

  3. Free body diagram - Wikipedia

    en.wikipedia.org/wiki/Free_body_diagram

    A free body diagram is not a scaled drawing, it is a diagram. The symbols used in a free body diagram depends upon how a body is modeled. [6] Free body diagrams consist of: A simplified version of the body (often a dot or a box) Forces shown as straight arrows pointing in the direction they act on the body

  4. Oxygen - Wikipedia

    en.wikipedia.org/wiki/Oxygen

    The free oxygen partial pressure in the body of a living vertebrate organism is highest in the respiratory system, and decreases along any arterial system, peripheral tissues, and venous system, respectively. Partial pressure is the pressure that oxygen would have if it alone occupied the volume.

  5. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. [69] This assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space.

  6. Lewis structure - Wikipedia

    en.wikipedia.org/wiki/Lewis_structure

    Another shorthand structural diagram is the skeletal formula (also known as a bond-line formula or carbon skeleton diagram). In a skeletal formula, carbon atoms are not signified by the symbol C but by the vertices of the lines. Hydrogen atoms bonded to carbon are not shown—they can be inferred by counting the number of bonds to a particular ...

  7. Atomic packing factor - Wikipedia

    en.wikipedia.org/wiki/Atomic_packing_factor

    The primitive unit cell for the body-centered cubic crystal structure contains several fractions taken from nine atoms (if the particles in the crystal are atoms): one on each corner of the cube and one atom in the center. Because the volume of each of the eight corner atoms is shared between eight adjacent cells, each BCC cell contains the ...

  8. Molecular model - Wikipedia

    en.wikipedia.org/wiki/Molecular_model

    A given atom would have solid and hollow valence spikes. The solid rods clicked into the tubes forming a bond, usually with free rotation. These were and are very widely used in organic chemistry departments and were made so accurately that interatomic measurements could be made by ruler.

  9. Atomic radius - Wikipedia

    en.wikipedia.org/wiki/Atomic_radius

    Diagram of a helium atom, showing the electron probability density as shades of gray. The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron.