Chemistry Review 🧪

Chemistry Review 🧪

Basic Review

Chemicals take up space and have mass. Exists as elements (pure form) and in chemical combinations called compounds (2+ elements, fixed ratio, different characteristics than their elements).

Elements ❌broken down into simpler substances. Composed of atoms.

Essential Elements (96% of an organism): H, C, N, O

Trace Elements (small need): Fe (Iron) and Zn (Zinc)

Atom 🤏 unit of matter w/ properties of element.

Protons ➕┊Electrons ➖┊Neutrons ⚫

#electron ☁️

Atomic number = protons

Protons + Neutrons = Atomic mass = average of mass of all isotopes belonging to that element

Isotopes

Isotopes are different forms of the same element; same # of protons, different # of neutrons.

• Carbon has 3 naturally occurring isotopes: Carbon 12 (6 ⚫), Carbon 13 (7 ⚫), Carbon 14 (8 ⚫)
• POSSIBLY radioactive
• Date fossils and medical tracing
  • Ingredients for making DNA are added to human cells. One ingredient is labeled with 3H, a radioactive isotope of hydrogen. 9 dishes of cells are incubated at different temperatures. The cells make new DNA, incorporating the radioactive tracer with 3H.
  • The cells are placed in test tubes, their DNA is isolated, and unused ingredients are removed.
  • A solution called scintillation fluid is added to the test tubes and they are placed in a scintillation counter. As the 3H in the newly made DNA decays, it emits radiation that excites chemicals in the scintillation fluid, causing them to give off light. Flashes of light are recorded by the scintillation counter.
  • The frequency of flashes, which is recorded as counts per minute, is proportional to the amount of the radioactive tracer present, indicating the amount of new DNA. In this experiment, when the counts per minute are plotted against temperature, it is clear that temperature affects the rate of DNA synthesis—most DNA was made at 35°C aka 95°F.

Energy

Electrons far from nucleus have ⬆️energy; they get excited and move up then down back a level.

Electrons of an atom ↕️(differ) in potential energy amounts.

Energy levels -> Electron shells

Electron Configuration, Chemical Properties and Bonding

The chemical behavior of an atom is defined by electron configuration and distribution.

Electron shell -> specific number of orbitals -> the 3D space where you find electron 90% of the time

Ions

• Atoms with fewer or more electrons than usual
• Charged atoms
• Occur from electron transfer between atoms
• Ca+ion
  • Posi+ively charged ions
• Anion
  • Negatively charged ions

Van der Waals and Molecular Structure

Van der Waals interactions

• Occur when temporary + and - regions of molecules interact.
• Weak interactions between molecules without breaking or making bonds.

Molecular shape - how biological molecules recognize and respond to each other

Structure - very important to the functioning in the living cell - determined atom valence orbital position