Elements, Atoms, and the Periodic Table

Comprehensive vocabulary flashcards covering basic chemical definitions, historical atomic models, subatomic particles, elemental abundances, periodic trends, and electronic structures from the Chapter 2 lecture transcript.

Element

A fundamental substance that cannot be broken down by chemical means into a simpler substance.

Atom

The smallest unit of an element that retains its properties and chemical behavior.

Subatomic Particles

The fundamental particles (protons, neutrons, and electrons) that compose an atom.

Dimitri Mendeleev

The chemist who designed the Periodic Table in 1869 to organize elements based on their properties.

Total Known Elements

There are currently 118 known elements in the periodic table.

Naturally Occurring Elements

There are 88 naturally occurring elements in nature.

Chemical Symbol

A one- or two-letter abbreviation used to represent an element.

Mass Percent of Top 10 Elements in Earth's Crust

Ten elements make up almost $99\%$ of the mass of the Earth's crust, seawater, and atmosphere.

Atmospheric Oxygen Content

Oxygen accounts for about $20\%$ of the Earth's atmosphere by mass.

Mass Percent of Oxygen in Earth's Crust

Oxygen makes up $49.2\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Silicon in Earth's Crust

Silicon makes up $25.7\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Aluminum in Earth's Crust

Aluminum makes up $7.5\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Iron in Earth's Crust

Iron makes up $4.7\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Calcium in Earth's Crust

Calcium makes up $3.4\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Sodium in Earth's Crust

Sodium makes up $2.6\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Potassium in Earth's Crust

Potassium makes up $2.4\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Magnesium in Earth's Crust

Magnesium makes up $1.9\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Hydrogen in Earth's Crust

Hydrogen makes up $0.9\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Titanium in Earth's Crust

Titanium makes up $0.6\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Chlorine in Earth's Crust

Chlorine makes up $0.19\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Phosphorus in Earth's Crust

Phosphorus makes up $0.11\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Manganese in Earth's Crust

Manganese makes up $0.09\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Carbon in Earth's Crust

Carbon makes up $0.08\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Sulfur in Earth's Crust

Sulfur makes up $0.06\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Barium in Earth's Crust

Barium makes up $0.04\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Nitrogen in Earth's Crust

Nitrogen makes up $0.03\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of Fluorine in Earth's Crust

Fluorine makes up $0.03\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Mass Percent of All Other Elements in Earth's Crust

All other remaining elements combined make up $0.49\%$ of the mass of the Earth's crust, oceans, and atmosphere.

Most Prevalent Elements in the Human Body

Oxygen ($65\%$), Carbon ($18\%$), and Hydrogen ($10\%$).

Mass Percent of Oxygen in Human Body

Oxygen accounts for $65\%$ of the total mass of the human body.

Mass Percent of Carbon in Human Body

Carbon accounts for $18\%$ of the total mass of the human body.

Mass Percent of Hydrogen in Human Body

Hydrogen accounts for $10\%$ of the total mass of the human body.

Mass Percent of Nitrogen in Human Body

Nitrogen accounts for $3\%$ of the total mass of the human body.

Mass Percent of Calcium in Human Body

Calcium accounts for $1.4\%$ of the total mass of the human body.

Mass Percent of Phosphorus in Human Body

Phosphorus accounts for $1\%$ of the total mass of the human body.

Trace Elements in Human Body

Elements present in tiny amounts that are crucial for life, such as chromium and copper.

Metals

Elements that are solids at room temperature (except mercury), shiny, good conductors of heat and electricity, malleable, and ductile.

Lustrous

The characteristic shiny physical appearance of metals.

Thermal and Electrical Conductivity

The ability of metals to efficiently transfer heat and electrical charge.

Malleable

The physical property of a metal enabling it to be hammered or shaped into thin sheets.

Ductile

The physical property of a metal allowing it to be drawn into thin wires.

Melting Point and Density of Metals

Physical properties that are generally high for most metallic elements.

Free State Metals

Metals that have low reactivity and can be found uncombined in nature, such as copper, gold, and silver.

Alloy

A homogeneous mixture formed by mixing metals together, such as brass, bronze, steel, and coinage metals.

Metal Reactivity

Metals readily combine with nonmetals to form compounds, but rarely combine with other metals.

Nonmetals

Elements that are not shiny, have fairly low melting points and densities, and are poor conductors of heat and electricity.

Nonmetal + Nonmetal Combination

Nonmetals combine with each other to form molecular compounds.

Nonmetal + Metal Combination

Nonmetals combine with metals to form ionic compounds.

Metalloids

Elements with properties intermediate between metals and nonmetals, positioned diagonally on the periodic table.

Metalloid Applications in Electronics

Certain metalloids, such as boron, silicon, and germanium, serve as semiconductor materials in electronic devices.

Noble Metals

Unreactive metals found in pure, uncombined forms in nature, specifically gold, silver, and platinum.

Composition of Air

A homogeneous mixture composed mainly of nitrogen and oxygen, existing as diatomic gaseous elements.

Diatomic Molecules

Molecules containing exactly two chemically bonded atoms of the same or different elements.

Seven Diatomic Elements

Elements existing naturally as diatomic molecules: Hydrogen ($\text{H}_2$), Oxygen ($\text{O}_2$), Fluorine ($\text{F}_2$), Bromine ($\text{Br}_2$), Iodine ($\text{I}_2$), Nitrogen ($\text{N}_2$), and Chlorine ($\text{Cl}_2$).

Normal State of Diatomic Hydrogen

Colorless gas ($\text{H}_2$).

Normal State of Diatomic Nitrogen

Colorless gas ($\text{N}_2$).

Normal State of Diatomic Oxygen

Colorless gas ($\text{O}_2$).

Normal State of Diatomic Fluorine

Pale yellow gas ($\text{F}_2$).

Normal State of Diatomic Chlorine

Greenish-yellow gas ($\text{Cl}_2$).

Normal State of Diatomic Bromine

Reddish-brown liquid ($\text{Br}_2$).

Normal State of Diatomic Iodine

Bluish-black solid ($\text{I}_2$).

Diatomic Elements in Compounds

When incorporated into compounds like water ($\text{H}_2\text{O}$), hydrogen and oxygen no longer exist as independent diatomic molecules.

Compound

A pure substance containing two or more elements chemically combined in a definite proportion by mass.

Chemical Decomposition of Compounds

The chemical breakdown of a compound into simpler substances or its constituent elements.

Whole Number Ratios in Compounds

Elements in compounds combine in fixed whole-number ratios of atoms.

Molecular Compounds

Compounds held together by covalent bonds, typically formed between nonmetal elements.

Ionic Compounds

Compounds held together by attractive forces between positive and negative charges, typically formed between a metal and a nonmetal.

Molecule

The smallest unchanged individual unit of a compound formed by two or more atoms.

Ion

A charged atom or group of atoms.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Known Compounds Count

More than 50 million compounds are currently known.

Physical Properties of Water

Clear/colorless liquid with a boiling point of $100\,^\circ\text{C}$ and a density of $1.00\,\text{g/mL}$.

Physical Properties of Hydrogen Peroxide

Pale blue liquid with a boiling point of $150\,^\circ\text{C}$ and a density of $1.44\,\text{g/mL}$.

Chemical Formula

An abbreviation for a compound containing symbols and ratios of the atoms of the constituent elements.

Subscript

Numbers written after element symbols in a chemical formula to specify the ratio of atoms present.

Law of Definite Composition

States that a compound always contains two or more elements chemically combined in a definite proportion by mass.

Law of Multiple Proportions

States that atoms of two or more elements may combine in different ratios to produce more than one compound.

Mass Composition of Water

$11.2\%$ Hydrogen and $88.8\%$ Oxygen by mass ($2\,\text{H} + 1\,\text{O}$).

Mass Composition of Hydrogen Peroxide

$5.9\%$ Hydrogen and $94.1\%$ Oxygen by mass ($2\,\text{H} + 2\,\text{O}$).

Percent Composition of Copper(I) Chloride

$64.2\%\,\text{Cu}$ and $35.8\%\,\text{Cl}$ ($\text{CuCl}$).

Percent Composition of Copper(II) Chloride

$47.3\%\,\text{Cu}$ and $52.7\%\,\text{Cl}$ ($\text{CuCl}_2$).

Percent Composition of Methane

$74.9\%\,\text{C}$ and $25.1\%\,\text{H}$ ($\text{CH}_4$).

Percent Composition of Octane

$85.6\%\,\text{C}$ and $14.4\%\,\text{H}$ ($\text{C}_8\text{H}_{18}$).

Percent Composition of Methyl Alcohol

$37.5\%\,\text{C}$, $12.6\%\,\text{H}$, and $49.9\%\,\text{O}$ ($\text{CH}_4\text{O}$).

Percent Composition of Ethyl Alcohol

$52.1\%\,\text{C}$, $13.1\%\,\text{H}$, and $34.7\%\,\text{O}$ ($\text{C}_2\text{H}_6\text{O}$).

Percent Composition of Glucose

$40.0\%\,\text{C}$, $6.7\%\,\text{H}$, and $53.3\%\,\text{O}$ ($\text{C}_6\text{H}_{12}\text{O}_6$).

Properties of Carbon Monoxide

Odorless, flammable, toxic gas ($\text{CO}$).

Properties of Carbon Dioxide

Odorless, nonflammable, suffocating gas ($\text{CO}_2$).

Properties of Sulfur Dioxide

Nonflammable gas with a suffocating odor ($\text{SO}_2$).

Properties of Ammonia

Colorless, nonflammable gas with a pungent odor ($\text{NH}_3$).

Properties of Carbon Tetrachloride

Nonflammable, dense liquid ($\text{CCl}_4$).

Properties of Nitrogen Dioxide

Reddish-brown gas that acts as an irritant ($\text{NO}_2$).

Physical Properties

Inherent characteristics of a substance that can be determined without altering its composition (e.g., color, taste, odor, density, melting point, boiling point).

Chemical Properties

Characteristics describing the ability of a substance to undergo a reaction with another substance or decompose.

Physical Change

A change in physical properties or state of matter without any change in chemical composition.

Chemical Change

A change in which new substances are formed with properties and compositions different from the original material.

Sawing Wood

A physical change where smaller wood pieces and sawdust are made from larger wood without changing chemical composition.

Heating Copper in Air

A chemical change where shiny copper metal turns black as copper(II) oxide is formed ($2\,\text{Cu} + \text{O}_2 \rightarrow 2\,\text{CuO}$).

Burning Wood

A chemical change in which wood undergoes combustion to produce ashes, gaseous carbon dioxide, and water while releasing heat and light.