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Californium is the chemical element with atomic number 98 and symbol . It is a actinide. All its isotopes are radioactive. Californium-252 is a neutron source because part of its decay occurs through spontaneous fission; that nuclear process is distinct from oxidation-state changes in its chemical compounds.[ref]
A chemical element in group 18 of the periodic table. Argon is a familiar example: its chemical inertness under many ordinary conditions makes it useful when a process needs a gas that does not readily react with the material being processed. Chemical inertness is a statement about conditions, rather than an assertion that no compound can exist.
Iridium is the chemical element with atomic number 77 and symbol . It is a transition metal. It is a dense platinum-group metal with strong corrosion resistance. Iridium-containing complexes and oxides can serve as catalysts, illustrating how oxidation state and coordination change the behavior of a chemically resistant bulk metal.[ref]
Polonium is the chemical element with atomic number 84 and symbol . All its isotopes are radioactive. Polonium-210 decays mainly by alpha emission, so a sample changes its nuclear composition with time even when no ordinary chemical reaction is occurring.[ref]
Caesium is the chemical element with atomic number 55 and symbol . It is a alkali metal. It readily forms . A specified hyperfine transition of caesium-133 defines the SI second, linking a reproducible atomic frequency with time measurement rather than with a mechanical clock.[ref]
Bismuth is the chemical element with atomic number 83 and symbol . It is a metal. The oxidation state is common. Natural bismuth is dominated by the extremely long-lived radioactive isotope bismuth-209, showing that everyday apparent stability and strict nuclear stability are not identical.[ref]
An alkali metal is a group-1 metallic element, such as lithium, sodium, or potassium; hydrogen is in group 1 but is not ordinarily classified as an alkali metal. These metals commonly form singly charged positive ions.
Their outer-electron configuration helps explain related chemical behavior across the group. Physical properties and detailed reactivity still vary, so group membership is an organizing pattern rather than identity of all properties.
An alkaline earth metal is a group-2 element, including magnesium, calcium, and barium. A common oxidation state is , associated with loss of two outer-shell electrons.
The resulting salts can nevertheless have very different solubilities and lattice properties. Comparing magnesium and calcium carbonates or hydroxides shows why periodic similarity does not eliminate the role of ion size, hydration, and crystal structure.
Gallium is the chemical element with atomic number 31 and symbol . It is a metal. Its melting point lies just above ordinary room temperature. Compounds such as gallium nitride are important semiconductors; their electronic properties arise from the compound lattice, not from the low melting point of elemental gallium.[ref]
Indium is the chemical element with atomic number 49 and symbol . It is a metal. It is a soft group-13 metal, commonly forming compounds. Indium-containing transparent conducting oxides and indium gallium nitride illustrate how the element contributes to optical and electronic materials without behaving as a free metal.[ref]
Germanium is the chemical element with atomic number 32 and symbol . It is a metalloid. Crystalline germanium is a semiconductor with a diamond-like crystal structure. Its electronic and infrared-optical properties connect chemical bonding in a solid with devices and spectroscopy.[ref]
Niobium is the chemical element with atomic number 41 and symbol . It is a transition metal. Niobium and several niobium alloys are used as superconductors. Its common chemistry also appears in oxides, including lithium niobate, whose optical and electrical behavior differs from that of the metal.[ref]
Radium is the chemical element with atomic number 88 and symbol . It is a alkaline earth metal. All its isotopes are radioactive. Its chemistry resembles that of barium, often favoring the state, while radioactive decay distinguishes its long-term behavior from an ordinary stable alkaline-earth salt.[ref]
Chromium is the chemical element with atomic number 24 and symbol . It is a transition metal. A chromium-rich passive oxide layer helps stainless steel resist corrosion. Chromium(III) and chromium(VI) compounds have substantially different bonding, reactivity, and environmental behavior, so an oxidation state is essential when discussing a chromium compound.[ref]
Plutonium is the chemical element with atomic number 94 and symbol . It is a actinide. It has no stable isotopes and exhibits several accessible oxidation states. Its solid has multiple structural phases, so both nuclear composition and crystal structure matter when specifying a plutonium sample.[ref]
Curium is the chemical element with atomic number 96 and symbol . It is a actinide. It has no stable isotopes and is produced through nuclear transformations. Its common trivalent chemistry helps organize its separation from other actinides, while its radioactive decay gives it physical behavior absent from a stable chemical analogue.[ref]
Erbium is the chemical element with atomic number 68 and symbol . It is a lanthanide. Erbium ions in glass can absorb and emit infrared light near telecommunications wavelengths. Erbium-doped optical amplifiers exploit these electronic transitions, linking an element's energy levels to long-distance optical communication.[ref]
Vanadium is the chemical element with atomic number 23 and symbol . It is a transition metal. It supports several oxidation states, producing differently colored ions in solution. Vanadium-containing alloys strengthen steel, while vanadium oxides participate in oxidation catalysis; the same element therefore plays distinct structural and chemical roles.[ref]
Lanthanum is the chemical element with atomic number 57 and symbol . It is a metal. The oxidation state dominates its chemistry. Lanthanum compounds occur in optical glasses and catalytic materials; the properties of those compounds should be distinguished from the reactive silvery elemental metal.[ref]
Thorium is the chemical element with atomic number 90 and symbol . It is a actinide. It has no stable isotopes, but thorium-232 is sufficiently long-lived to occur naturally. The oxidation state is characteristic of its chemistry, distinguishing it from the more usual chemistry of many neighboring f-block elements.[ref]
Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 2. You can publish local OurBigBook lightweight markup files to either OurBigBook.com or as a static website.
Figure 3. Visual Studio Code extension installation.
Figure 5. . You can also edit articles on the Web editor without installing anything locally. Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension. 
- Infinitely deep tables of contents:
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