Unit 1: Search for Life - Chemistry and Properties of Life

Comprehensive vocabulary flashcards covering the Search for Life unit, including atomic structure, chemical bonding, water properties, ionic ratios, and spectroscopic methods.

Octet Rule

The principle that elements will give or take electrons to fill their outer energy level with 8 electrons (with phosphorus noted as an exception).

Lewis Dot Structures

A shorthand visual way to represent the valence electrons of an atom.

Periodic Table

A chart that organizes elements and can be used to predict patterns, including valence electrons and ion formation.

Chemical Bond

The way atoms attach to each other.

Covalent Bond

A bond formed when nonmetal atoms share valence electrons, typically forming substances that are gases at room temperature with low melting and boiling points.

Ionic Bond

A chemical bond formed between ions of a metal and a nonmetal when electrons are transferred (given or taken).

Polar Covalent Bond

A bond between nonmetals where electrons are shared unequally, producing partial charges, moderate melting and boiling points, and substances that are typically liquids near or at room temperature.

Polarity

The separation of electric charges within a molecule.

Electronegativity

How strongly an atom pulls on another atom's electrons.

Water Molecule Polarity

The unequal sharing of electrons in $H_2O$ where oxygen pulls more strongly on electrons than hydrogen, creating partial negative ($\delta^-$) and partial positive ($\delta^+$) charges.

Exoplanet

A planet located outside of our solar system.

Spectroscopy

The measurement of energy produced from matter; it provides a unique spectrum for each element or compound as electrons absorb energy, move energy levels, and emit light upon returning.

Ion

A charged particle formed when an atom gains or loses electrons.

Cations

Positively charged ions formed when atoms lose electrons (e.g., $Na^+$, $Ca^{2+}$).

Anions

Negatively charged ions formed when atoms gain electrons (e.g., $Cl^-$, $O^{2-}$).

Ionic Compound

A compound composed of cations and anions held together by ionic bonds; they exist as solids at room temperature and have high melting and boiling points.

Electrolyte

A substance with an electric charge formed when a salt dissolves in water, releasing ions that move and conduct electricity to support biological functions like nerve communication.

Salt

A substance formed from a positive ion (cation) and a negative ion (anion).

Solute

The substance that is being dissolved or ionized in a solution.

Solvent

The substance that does the dissolving in a solution (usually water).

Solution

A homogeneous mixture formed by combining a solute and a solvent.

Valence Electrons

Electrons residing in the outermost ring of an atom that govern bonding and determine the ratio in which elements combine.

Energy Levels

The rings or orbitals of electrons surrounding an atom's nucleus, where rings located further out contain more energy.

CHONPS

The six essential elements (Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, Sulfur) required to build living macromolecules like carbohydrates, proteins, and DNA/RNA.

Arsenic-for-Phosphorus Substitution

A scientific hypothesis tested in DNA; although arsenic has the same number of valence electrons as phosphorus, arsenic could not substitute for phosphorus, and the study could not be replicated.

Hydrogen Sulfide ($H_2S$)

A compound tested as a substitute for water that shares a bent shape and polar covalent properties, yet lacks all of water's critical life-supporting properties.

Lithium Oxide ($Li_2O$)

A compound evaluated as a potential water substitute that instead forms an ionic solid with high melting and boiling points.

Ionic Bonding Ratio

The fixed ratio in which metal cations and nonmetal anions combine based on valence electron transfers to form neutral salts (e.g., $1:1$ for $NaCl$, $2:1$ for $Na_2O$, $1:3$ for $AlCl_3$).