Aaron J. Powner, M.Ed.
High School Science Teacher
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Lavoisier - Late 1700s
French scientist, Antoine Lavoisier, compiled the earliest table of known elements (33 at the time)
Early 1800s
Discovery that electricity can break down compounds into their components.
Development of the spectrometer, which can identify elements.
- Diagram - prisms and light
- Diagram - electromagnetic spectrum
- Diagram - spectroscopy
- Diagram - manual vs. digital spectroscopy
- Diagram - sample spectrogram (absorption and emission)
- Diagram - emission spectrograms of common elements
Newlands 1864
English chemist John Newlands noticed that when elements are arranged by increasing atomic mass, their properties repeat every eight element, similar to octaves in musical theory. He proposed that this pattern be called the "Law of Octaves."
Meyer and Mendeleev 1869
German chemist Lothar Meyer and Russian chemist demonstrated a connection between atomic mass and the properties of elements. Mendeleev's periodic table was a breakthrough because it predicted the chemical properties of undiscovered elements. There was a flaw in Mendeleev's periodic table. When elements are organized by atomic mass, a few of them wind up in the wrong groups of elements, mismatching their physical and chemical properties.
Mosely 1913
English chemist Henry Mosely discovered that each element has a unique number of protons. Mosely found that organizing the periodic table of elements by their atomic numbers corrects Mendeleev's flaw. The elements they always fall into the right groups when arranged by proton number.
Periodic Law
Mosely's discovery finalized what we now call the Periodic Law, which states that there is a periodic repetition of chemical and physical properties of the elements when they are arranged by increasing atomic number.
Anatomy - elements are arranged into columns and rows in order of atomic number (protons)
Groups/Families - numbered columns, often named by the period 2 element of the group, alchemy names still apply
Periods - numbered rows, each period adds a new electron shell
Condensed Periodic Table vs. Expanded Periodic Table
Representative Elements vs. Transition Elements
Common Group/Family Properties
Alkali Metals - [Li] Lithium Family, Group 1
- tend to lose one electron to form 1+ ions
- form ionic compounds (salts, or alkali halides) in reactions with halogens
- sodium and potassium ions are important ingredients of body fluids (electrolytes)
Alkaline Earth Metals - [Be] Beryllium Family, Group 2
- tend lose two electrons to form 2+ ions
- alkaline earth compounds form many common minerals such as calcium carbonate, magnetite, and gypsum
- pure elements can be separated by heating, but do not occur in nature in pure form
- like sodium and potassium, calcium and magnesium are important electrolytes
- calcium phosphates form bones and teeth
- magnesium is a key component of chlorophyll, the molecule in green plants that allows photosynthesis
Transition Elements - Groups 3 to 12 and the Lanthanide and Actinide Series
- typically high melting points
- have several oxidation states (multiple stable ions)
- typically form colored compounds
- often paramagnetic
- iron and titanium are the most abundant of the transition elements
- many catalysts for industrial reactions involve transition elements
- lanthanides are rare earth elements
- actinides are all radioactive
Coinage Metals - [Cu] Copper Family, Group 11
- used historically in alloys to mint coins of actual monetary worth
- copper, silver, and gold
Volatile Metals - [Zn] Zinc Family, Group 12
- zinc, cadmium, and mercury are widely used in electrical and electronic applications, as well as in many useful alloys
- mercury is known for being liquid at room temperature
- zinc is very important in the biochemistry of living organisms. However, cadmium and mercury are highly toxic
Icosagens - [B] Boron Family, Group 13, Triels
- tend to lose three electrons to form 3+ ions
- at very high voltages, aluminum conducts electricity with very little resistance
Crystallogens - [C] Carbon Family, Group 14, Tetrels
- this group shows the greatest chemical versatility
- these could gain or lose four electrons to form 4+/4- ions, but often have a preference for covalent bonding
- carbon is the basis of all organic chemistry and forms more compounds than any other element except hydrogen
Pnictogens - [N] Nitrogen Family, Group 15
- tend to gain three electrons to form 3- ions
- nitrogen is the most important element of this group. Diatomic nitrogen is the main ingredient in Earth's atmosphere. Legumes and blue-green algae transform nitrogen into ammonia (nitrogen fixation), which is an essential plant nutrient (fertilizer).
- phosphorous is also an essential plant nutrient. With oxygen, it forms phosphates used in fertilizers.
- calcium phosphates are the major component of bones and teeth
Chalcogens - [O] Oxygen Family, Group 16
- tend to gain two electrons to form 2- ions
- oxygen makes up nearly half of the Earth's crust by mass, mainly in the form of silicates
- photosynthesis in plants produced enough oxygen over geologic time to enrich Earth's atmosphere to 21%
- sulfur is mined for the industrial use of sulfuric acid
Halogens - [F] Fluorine Family, Group 17
- halogens means "salt formers"
- tend to gain one electron to form 1- ions
- all halogens are extremely reactive chemically, increasing in strength moving upward to fluorine, the most reactive element in the periodic table
- fluorine is used in dentistry and oral hygiene products due to its ability to increase the strength of tooth enamel in small doses. In large doses it warps teeth and can be toxic.
- at room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid
- these form diatomic molecules in the pure state
- all halogens are poisonous. Chlorine gas and chlorine compounds have been used as chemical weapons. In small concentrations, chlorine is used to disinfect drinking water and swimming pools
Noble Gases - [He] Helium Family, Group 18, Aerogens
- noble gases have closed electron shells (filled to stable capacity, 8 electrons)
- these are unreactive chemically
- helium, neon, argon, and krypton are used in decorative lighting called "neon lights"
- argon is used to fill incandescent light bulbs to prevent evaporation and oxidation of the tungsten filaments, increasing bulb life
- xenon is used in electronic flash tubes (e.g. cameras)
- density of noble gases increases with increasing molecular mass. Helium is about one seventh the density of air and is used in balloons. Xenon is about five times the density of air.
- noble gases are often used in fire suppression systems
Metalloids - Boron (Be), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te)
- chemical and physical properties are a mixture of (or somewhere between) metals and nonmetals
- less commonly recognized as metalloids: Carbon (C), Aluminum (Al), Selenium (Se), Polonium (Po), Astatine (At)
- physically, metalloids usually have a metallic appearance but are brittle. They are also fair conductors of electricity
- chemically, they mostly behave as "weak" nonmetals but can form alloys with other metals
- commonly used in glass, alloys, fire retardants, and semiconductors. The electrical properties of silicon (Si) and germanium (Ge) make them especially useful in solid-state electronics, computer chips, and optical data storage.
Relative Abundance of Elements on Earth
Electron Configuration - Orbital Blocks
Theodor Benfey's Element Spiral (1964)
https://www.khanacademy.org/science/chemistry/periodic-table
The NEW Periodic Table Song, by AsapScience | YouTube | Direct Stream |
Challenge Option A: If you sing this song karaoke style to me individually or in groups, you will receive 10% bonus credit on the exam for this unit.
Challenge Option B: If you memorize and sing this accompanied only by the music, you will be guaranteed at least a passing grade of 60%... you cannot fail.
The Elements Song - written by Tom Lehrer, a professor of music and mathematics University of California, Santa Cruz. He performed as a musical humorist in the 1950s and 1960s. Download the lyrics.
