BILD 1: The Cell - Introduction to Matter and Bonds

Vocabulary practice flashcards covering Chapter 2 concepts from BILD 1: The Cell, including matter, elements, atomic structure, electronegativity, chemical bonding, and emergent properties.

Matter

Anything that takes up space and has mass, consisting of pure chemical elements and combinations of elements.

Atom

The smallest unit of matter that retains the properties of an element, consisting of three primary subatomic particles: protons, neutrons, and electrons.

Element

A pure substance that consists of only one type of atom, is identified by its atomic number (number of protons), and cannot be broken down into other substances by chemical reactions.

Atomic Number

The number of protons in an atom's nucleus that defines the identity of an element (for example, oxygen has an atomic number of $8$).

Isotopes

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

Erwin Schrödinger's Atomic Model

The $1926$ quantum mechanical atomic model that depicts electrons in probabilistic 3D electron clouds rather than fixed planar orbits.

Electronegativity

The capability of an atom to attract electrons toward itself within a chemical bond.

Periodic Electronegativity Trend

The trend where electronegativity increases going across a period as nuclear charge increases and atomic radius decreases, creating a stronger attraction between the nucleus and bonding electrons.

Nonpolar Covalent Bond

A covalent bond formed between atoms with equal or nearly equal electronegativity (difference less than $0.5$), resulting in equal sharing of electrons (e.g., $H_2$ or $Cl_2$).

Polar Covalent Bond

A covalent bond formed between atoms differing moderately in electronegativity (difference between $0.5$ and $1.7$), causing unequal sharing of electrons and creating partial positive ($\delta+$) and partial negative ($\delta-$) charges.

Ionic Bond

A chemical interaction formed when a large difference in electronegativity (greater than $1.7$) causes one atom to completely steal or strip an electron from another atom instead of sharing it, forming oppositely charged ions.

Formica rufa

Wood ants that utilize chemistry by producing and spraying formic acid ($CH_2O_2$) to ward off enemies.

Formic Acid ($CH_2O_2$)

A compound consisting of carbon, hydrogen, and oxygen, whose acidic sting occurs because an oxygen atom attracts hydrogen's electron and releases an $H^+$ ion.

Major Human Body Elements

The four chemical elements—oxygen ($65.0\%$), carbon ($18.5\%$), hydrogen ($9.5\%$), and nitrogen ($3.3\%$)—that make up $96.3\%$ of human body mass.

Trace Elements

Essential chemical elements that make up less than $0.01\%$ of body mass, including boron, chromium, cobalt, copper, fluorine, iodine, iron, manganese, molybdenum, selenium, silicon, tin, vanadium, and zinc.

Potential Energy of Electrons

The stored energy that electrons possess due to their distance from the nucleus, which increases in higher electron shells located farther from the nucleus.

Valence Electrons

Electrons residing in an atom's outermost shell (valence shell) that primarily determine its chemical behavior and reactivity.

Valence

The bonding capacity of an atom, typically corresponding to the number of unpaired electrons in its valence shell (e.g., hydrogen = $1$, oxygen = $2$, nitrogen = $3$, carbon = $4$).

Chemical Bonds

Attractions that hold atoms close together when atoms with incomplete valence shells share or transfer valence electrons.

Molecule

A structure formed when two or more atoms are held together by covalent bonds, whether composed of identical elements (e.g., $O_2$, $H_2$, $N_2$) or different elements.

Compound

A substance composed of two or more different elements chemically bonded together in a fixed ratio (e.g., $CO_2$, $NaCl$).

Emergent Properties (in Compounds)

Unique characteristics of a compound that differ distinctly from those of its component elements, such as edible sodium chloride ($NaCl$) forming from soft reactive sodium metal ($Na$) and toxic chlorine gas ($Cl_2$).