Chemical Foundations of Biology and Water Properties Flashcards

Vocabulary flashcards covering atomic structure, chemical bonding types, electronegativity, polar and nonpolar interactions, and the chemical properties of water.

Major Weight-Contributing Elements

The four elements—carbon, hydrogen, oxygen, and nitrogen—that make up the vast majority of the weight of living organisms.

Nucleus

The central core of an atom that contains protons and neutrons.

Valence Electrons

Electrons located in the outermost energy level of an atom that determine whether the atom is stable or chemically reactive.

Noble Gases

Chemically inert elements, such as neon, that have a completely filled outermost energy shell.

Cation

A positively charged ion formed when an atom loses one or more negative electrons (e.g., sodium losing an electron).

Anion

A negatively charged ion formed when an atom accepts one or more negative electrons (e.g., chlorine gaining an electron).

Ionic Bond

An attractive electrostatic force between oppositely charged ions (cations and anions); while strong chemically, it is easily disrupted in the presence of water.

Crystal Lattice

A three-dimensional repeating array formed when ionic bonds extend in all directions, as seen in table salt ($NaCl$).

Covalent Bond

A chemical bond formed when non-metal atoms share pairs of valence electrons to achieve stability.

Molecule

A particle formed when two or more atoms come together through chemical bonds.

Compound

A specific type of molecule composed of two or more different types of atoms (e.g., carbon dioxide).

Methane

A molecule composed of one carbon atom covalently bound to four hydrogen atoms, forming a tetrahedral shape.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between atoms, characterized by an electronegativity difference of $0.4$ or less.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally, creating partial positive and partial negative charges; occurs when the electronegativity difference is $0.5$ to $1.7$.

Electronegativity

An atom's tendency to attract electrons, which increases moving up a period and across groups on the periodic table.

Fluorine

The element with the highest electronegativity on the periodic table.

Hydrophilic

"Water loving"; describes polar or charged molecules that readily associate with water.

Hydrophobic

"Water fearing"; describes nonpolar substances that aggregate together away from water.

Hydrogen Bond

A non-covalent attractive force occurring between a partially positive hydrogen atom in a polar covalent bond and a neighboring electronegative atom with a partial negative charge.

Van der Waals Forces

Weak, non-covalent electrical attractions between neutral molecules occurring at a precise "Goldilocks" distance where electron clouds and nuclei interact without repelling.

Water Composition in Humans

An adult human is composed of $60$ percent water, located inside cells, surrounding tissues, and within blood.

Density Anomaly of Water

The property of water being less dense in solid form (ice) than in liquid form, because lower temperatures slow molecular movement and lock hydrogen bonds into a more open structure, allowing ice to float.