Chapter 2: Chemical Basis of Life - Atoms, Molecules, and Water

Vocabulary flashcards covering atomic structure, electron orbitals, chemical bonds, electronegativity, and properties of water from Chapter 2 lecture notes.

Atomic Orbital

A travel path or region within an electron energy shell where electrons are located around the nucleus.

First Electron Shell

The innermost electron energy level containing $1$ orbital that holds up to $2e^-$.

Second Electron Shell

An electron energy level containing $1s$ and $3p$ orbitals, holding up to $8$ total $e^-$.

s Orbital

An atomic orbital capable of holding up to $2e^-$.

p Orbital

An atomic orbital capable of holding up to $6e^-$ across $3$ different orientations, with $2e^-$ per orientation.

Valence Electrons (VE)

Electrons residing in the outermost shell that possess the most energy and are available to form bonds.

Periodic Table Columns

Columns read left to right on the periodic table that indicate the number of valence electrons, resulting in similar chemical reactivity.

Ions

Very reactive atoms or molecules that have lost or gained electrons.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Octet Rule

The rule stating that atoms seek stable outer shells, filled at $8e^-$ for the $2\text{nd}$ and $3\text{rd}$ shells, and $2e^-$ for Hydrogen and the $1\text{st}$ shell.

Electronegativity

The measure of how strongly an atom pulls on shared electrons, increasing from left to right and bottom to top on the periodic table.

Nonpolar Covalent Bond

A bond where electrons are shared equally between atoms due to an electronegativity difference of $\le 0.4$ (e.g., C-C, C-H, N-N, O-O).

Polar Covalent Bond

A bond where electrons are shared unequally due to an electronegativity difference between $0.4$ and $1.8$, creating partial charges (e.g., N-H, N-C, O-H, O-C).

Ionic Bond

A chemical bond formed between a metal and a nonmetal with an electronegativity difference $> 1.8$, where electrons are transferred rather than shared, held together by electrostatic attraction.

Hydrogen Bonds

Interactions formed between molecules with polar covalent bonds that are individually weak but collectively strong.

Van der Waals Interactions

Weak interactions that occur between nonpolar molecules.

Hydrophobic Interactions

Interactions between nonpolar molecules that do not dissolve in or interact with water.

Hydrophilic Substances

Polar or ionic substances that interact with and dissolve in water.

Hydrophobic Substances

Nonpolar substances that are insoluble in water and do not interact with it.

Isotopes

Atoms of the same element that differ in their number of neutrons.

Cohesion and Adhesion

Properties of water where water molecules stick to each other (cohesion) or stick to other surfaces (adhesion).

High Specific Heat of Water

The property of water that enables it to resist temperature changes.

Atomic Number

The defining number of protons in an atom used to organize elements on the periodic table.