Applied Agricultural Chemistry I: Atomic Theory, Chemical Bonding, and Matter

Vocabulary practice flashcards covering fundamental chemistry, atomic theory, chemical nomenclature, bonding, VSEPR geometry, and agricultural applications.

Element

The most basic form of matter that exists under ordinary conditions and cannot be broken down into simpler substances, with all matter in the universe composed of fewer than 90 unique varieties.

Compound

A unique substance composed of two or more chemical elements that are chemically combined in definite proportions.

Abundance of Elements in Earth's Crust

The elemental distribution of the Earth's crust, in which oxygen ($45.2\%$) and silicon ($27.2\%$) make up the vast majority, followed by aluminum ($8\%$), iron ($5.8\%$), calcium ($5.06\%$), magnesium ($2.77\%$), sodium ($2.32\%$), potassium ($1.68\%$), and titanium ($0.86\%$).

Plum Pudding Model

An atomic model proposed in 1897 by J.J. Thomson following the discovery of electrons ('corpuscles'), which envisions the atom as a positively charged sphere embedded with negatively charged electrons like raisins in a pudding.

Rutherford's Gold Foil Experiment

A 1911 experiment by Ernest Rutherford that fired positively charged alpha particles at a thin gold sheet, demonstrating that atoms consist primarily of empty space with a tiny, dense, positively charged center called the nucleus.

Bohr Model

An atomic model formulated in 1913 by Niels Bohr that placed electrons into definite orbits or quantized energy levels located at specific distances from the nucleus.

Electron Cloud

A region in the modern wave mechanics model where electrons are most likely to be located, with lower-energy electrons found closest to the nucleus and higher-energy electrons found in outer regions.

Atomic Number ($Z$)

The number of protons in the nucleus of an atom, which uniquely establishes the elemental identity of the atom.

Mass Number ($A$)

The total number of nucleons (protons and neutrons combined) residing in the nucleus of an atom.

Isotope

Atoms of the same element that share the same atomic number ($Z$) but possess different mass numbers ($A$) due to varying numbers of neutrons.

Atomic Mass Unit (amu)

A standard unit of mass defined as exactly $\frac{1}{12}$ the mass of a carbon-12 ($^{12}\text{C}$) atom.

Agricultural Chemistry

The study of chemistry in relation to agricultural systems, focusing on agricultural production, the processing of crop and animal products, and the environmental interactions among plants, animals, and soil.

Feed Component Analysis

A laboratory partition of livestock feed dividing total dry matter into organic matter (crude protein, ether extract/crude fat, crude fiber, and nitrogen-free extract) and inorganic matter (minerals or ash).

Calcareous Soil

A soil type dominated by calcium ($\text{Ca}$) with an alkaline $\text{pH}$ ranging between $7.1$ and $8.2$.

Sodic Soil

A soil class dominated by sodium ($\text{Na}$) and characterized by free salts and strongly alkaline conditions.

Acid Rain

Precipitation with elevated levels of hydrogen ions resulting from atmospheric reactions of emitted sulfur dioxide ($\text{SO}_2$) and nitrogen oxides ($\text{NO}_x$) to form sulfuric acid ($\text{H}_2\text{SO}_4$) and nitric acid ($\text{HNO}_3$).

Ozone-Depleting Substances (ODS)

Chemical agents—including chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl chloroform, and hydrochlorofluorocarbons (HCFCs)—that cause the breakdown of the stratospheric ozone layer.

Metal Chelation

A preservative mechanism whereby compounds such as ethylenediaminetetraacetic acid (EDTA), citrates, and gluconates bind transition metal ions ($\text{Fe}$, $\text{Cu}$, $\text{Mn}$) into stable complexes, preventing catalytic oxidative degradation of nutrients.

Extensive Property

A physical property, such as mass or volume, whose measurable value directly depends upon the quantity of matter present.

Intensive Property

A physical property, such as density, color, clarity, melting point, or boiling point, whose value is independent of the amount of substance present.

Density

An intensive physical property representing the ratio of a sample's mass to its volume ($\text{density} = \frac{\text{mass}}{\text{volume}}$), expressed in units such as $\text{g/mL}$ or $\text{g/cm}^3$.

Covalent Bond

A chemical bond established between nonmetal atoms through the mutual sharing of one or more electron pairs.

Structural Formula

A chemical representation indicating the specific sequence, connectivity, and arrangement of bonded atoms within a molecule.

Polyatomic Ion

A covalently bonded group of atoms that carries an overall net positive or negative electrostatic charge due to an imbalance between total protons and total electrons.

Ionic Bond

The electrostatic force of attraction that holds oppositely charged cations and anions in a rigid three-dimensional crystal lattice.

Octet Rule

The guideline stating that representative elements tend to lose, gain, or share electrons to attain an outer shell of eight valence electrons matching the electron configuration of a noble gas.

Valence Electrons

The outer $s$ and $p$ electrons of an atom of a representative element that participate directly in the formation of chemical bonds.

Electronegativity

The relative ability of an atom participating in a covalent bond to attract shared bonding electrons toward itself, scaled from metals up to fluorine at $4.0$.

Polar Covalent Bond

A covalent bond formed between atoms with different electronegativities ($\Delta\text{EN} < 1.8$), resulting in an unequal sharing of electrons and the generation of partial electrostatic charges ($\delta^+$ and $\delta^-$).

VSEPR Theory

Valence Shell Electron-Pair Repulsion theory, which determines molecular shapes based on the principle that electron groups (bonds and lone pairs) surrounding a central atom repel each other to achieve maximum spatial separation.

Molecular Dipole

The net vector sum of all individual bond dipoles across a molecule, which cancels to zero in symmetrical geometries bearing identical terminal atoms.

Periodic Law

The principle stating that the physical and chemical properties of elements recur periodically when the elements are arranged in order of increasing atomic number.

Alkali Metals

The elements of Group IA (excluding hydrogen) that possess one valence electron and readily lose it to form cations with a $+1$ charge.

Halogens

The nonmetal elements of Group VIIA that have seven valence electrons and readily gain one electron to form anions with a $-1$ charge.

Stock System

The IUPAC nomenclature method that indicates the positive charge of a multivalent metal cation using a Roman numeral placed in parentheses immediately following the element's name.

Oxyacid

An acid formed by combining hydrogen with a polyatomic oxyanion, named by altering the anion's -ate suffix to -ic acid or -ite suffix to -ous acid.

Aufbau Principle

The rule dictating that electrons fill available atomic subshells of the lowest energy before occupying subshells of higher energy.

Pauli Exclusion Principle

The quantum physical principle asserting that no two electrons occupying the same atomic orbital can possess identical spins.

Hund's Rule

The rule establishing that electrons occupy degenerate orbitals within the same subshell individually with parallel spins before any orbital receives a second electron.