Levels of Organization: The Chemical Level of Atoms and Molecules

Matter and the Elements of the Human Body

• Definition of Matter: Matter is defined as anything that takes up space and possesses mass.

• Forms of Matter:     - Naturally Occurring States: In the standard world, matter exists in three primary states: solids, liquids, and gases.     - Plasma: This is another known form of matter found in the universe.     - Artificial Matter: Scientists recently discovered a way to artificially create a new form of matter by making photons behave like a solid.         - The speaker notes that this discovery generated public excitement because it mimics the conceptual technology of "lightsabers."

• Elements: Matter is composed of elements, which are organized on the Periodic Table.     - Elements are organized by their number of protons and other physical/chemical properties.     - Different types of matter result from various combinations of these elements.     - The atom is the most basic unit of an element.

• Major Elements in the Human Body: Approximately $95\%$ of the human body is comprised of just four elements:     - Oxygen     - Carbon     - Hydrogen     - Nitrogen

• The "Carbon Unit" Concept (Star Trek Anecdote):     - In the late $1970s$, following the success of Star Wars, a Star Trek motion picture was released to capitalize on the science fiction phenomenon (though the original TV show dates back to the $1960s$).     - The plot involved a new female character who disappeared after the Enterprise was attacked, only to return as an intermediary for an entity called Viger (V'ger).     - This character had a robotic speaking pattern, wore a short mini-dress, and had a glowing orange circle on her throat.     - She referred to characters like Kirk and Spock as "carbon units" because the entity Viger had analyzed them and determined their biological composition was primarily carbon.     - Organic Chemistry: Human molecules are considered organic specifically because they contain carbon.

The Structure of the Atom

• Definition of an Atom: An atom is the smallest unit of an element that still behaves like that element and retains its specific properties (e.g., how an atom of gold or oxygen interacts with other atoms).

• Scale of an Atom: Atoms are infinitesimally small.     - Analogy: If you magnify the entire Earth down to the size of a speck of dust, and then magnify that speck of dust down by the same scale, you reach the size of an atom.

• Subatomic Particles: Atoms consist of three primary particles: protons, neutrons, and electrons.

Protons

• Location: Found within the nucleus (center) of the atom.

• Size/Mass: They are relatively large compared to electrons and contribute significantly to the atom's mass.

• Electrical Charge: Positively charged ($+$).

• Relevance: Protons define the identity of the element.     - Atomic Number: The number of protons is the atomic number.     - If an atom has $6$ protons, it is Carbon. If it is Carbon, it must have $6$ protons.     - Oxygen has $8$ protons.

Neutrons

• Location: Found in the nucleus alongside protons.

• Size/Mass: Roughly the same size/mass as protons.     - Mass Number: Calculated by adding the number of protons and the number of neutrons ($\text{Protons} + \text{Neutrons}$).     - Example: Carbon with $6$ protons and $6$ neutrons has a mass number of $12$.

• Electrical Charge: Neutral; they have no charge.

• Relevance: Neutrons determine the isotope of the element.     - Isotopes: Different formats of the same element (same proton count, different neutron count).     - Example: Carbon-12 (standard) vs. Carbon-13 (used in dating/scientific analysis).

Electrons

• Location: Electrons orbit the nucleus at various distances rather than being inside it.

• Energy Levels/Shells: These orbits are referred to as shells, orbitals, or energy levels.     - First Shell: Holds a maximum of $2$ electrons. (Elements like Hydrogen have $1$; Helium has $2$).     - Second Shell: Holds a maximum of $8$ electrons.     - Third Shell: Holds a maximum of $8$ electrons.     - Shells must be filled from the inside out; the outer shell will not begin filling until the inner shells are full.

• Size/Mass: Massively smaller than protons (infinitesimal mass), so they are ignored when calculating mass number.

• Electrical Charge: Negatively charged ($-$).     - The negative charge of a single electron is exactly equal in magnitude to the positive charge of a single proton, allowing them to balance each other out.

• Atomic Neutrality: In a typical atom that has not gained or lost electrons, the number of protons equals the number of electrons, making the overall charge of the atom neutral.

• Relevance: Electrons drive chemical reactivity.     - Stability: Atoms are most stable ("happiest") when their outer shell is full ($8$ electrons for most).     - Carbon has $4$ electrons in its outer shell; because it wants $8$, it is highly reactive and seeks to form bonds with other atoms to fill that shell.

Molecules and Compounds

• Molecule: Formed whenever two or more atoms are bonded together.     - Example: $O_2$ (two oxygen atoms bound together).

• Compound: A specific type of molecule that contains at least two different elements.     - Example: $CO_2$ (Carbon Dioxide) contains one carbon and two oxygens.     - Rule: All compounds are molecules, but not all molecules are compounds.

• Mole: A unit of measurement used to quantify the amount of an atom or molecule.     - Millimolar: One thousandth of a mole ($10^{-3}$, commonly used in smaller scale measurements).

• Standard Notation: A shorthand way to represent the composition of molecules.     - $H_2O$: Water; consists of $2$ hydrogen atoms and $1$ oxygen atom.     - $CO_2$: Carbon dioxide.     - $CO$: Carbon monoxide.     - $HCO_3^-$: Bicarbonate; consists of $1$ hydrogen, $1$ carbon, and $3$ oxygen atoms, with an overall negative charge.

Additional Resources

• IBM Research: The tech company IBM is involved in the manipulation of atoms.

• "A Boy and His Atom": A notable video created by IBM using atoms to create animation.