Lecture Notes: Chemistry Basics — Electron Shells, Valence, Ionic Bonds, Redox, and Cellular Energy

Vocabulary-style flashcards to review key concepts from the lecture: electron shells, valence electrons, ionic bonds, redox, energy storage in cells, and related periodic-table ideas.

Electron shell

Concentric regions around an atom where electrons reside; filled from the inside out; the number of shells varies by element.

Valence electrons

Electrons in the outermost shell that determine bonding and chemical reactivity.

Lithium (Li) — two electron shells

A 1A element with its inner shell filled and one electron in its outer valence shell.

Beryllium (Be) — valence electrons

Has 2 electrons in its outer valence shell.

Sulfur (S) — valence and shells

Has three electron shells with 6 valence electrons and needs 2 more to complete its outer shell.

Oxygen (O) — valence and electronegativity

Has 6 valence electrons, needs 2 to complete its shell, and is highly electronegative (electron hog).

Ionic bond

Bond formed by transfer of electrons between atoms, often involving Group 1A and Group 2A elements, resulting in ions.

Electronegativity (electron hog idea)

Tendency of an atom to attract electrons in a bond; oxygen is a strong example of an electronegative atom.

Water (H2O)

Molecule with oxygen bonded to two hydrogens; a key polar molecule in biology; depicted in the lecture as an illustration of electron distribution.

Glucose storage in plants

Plants store excess glucose as starch; potatoes store energy in the form of starch.

ATP and phosphate transfer

ATP donates a phosphate group to another molecule to supply energy for cellular processes (phosphorylation energy transfer).

Redox reactions

Short for oxidation-reduction reactions; involve transfer of electrons and changes in oxidation states.

Neutrons and mass number

Neutrons are calculated as neutrons = atomic mass (A) − protons (Z); N = A − Z.

Noble gases

Elements with full outer electron shells; largely inert and located on the far right of the periodic table.

Reaction rate factors: temperature and particle size

Reaction rate is affected by temperature (energy of collisions) and particle size (surface area/frequency of collisions).