Dentistry

50 shades whiter: What you should know about teeth whitening

The effect of teeth whitening was discovered quite by accident. In the past, dentists tried to treat gum disease with mouth rinses containing hydrogen peroxide. They noticed teeth became whiter over time following use of ...

Immunology

Breast milk and babies' saliva shape oral microbiome

Newborn breastfed babies' saliva combines with breastmilk to release antibacterial compounds that help to shape the bacterial communities (microbiota) in babies' mouths, biomedical scientists have found.

Oncology & Cancer

Why high-dose vitamin C kills cancer cells

Vitamin C has a patchy history as a cancer therapy, but researchers at the University of Iowa believe that is because it has often been used in a way that guarantees failure.

Dentistry

Should I use mouthwash?

A mouthwash or therapeutic rinse can complement brushing and flossing, but it's not a license to abandon proven oral health care. Here are a few things to consider before incorporating one into your daily routine.

Medical research

Gray hair and vitiligo reversed at the root

Hair dye manufacturers are on notice: The cure for gray hair is coming. That's right, the need to cover up one of the classic signs of aging with chemical pigments will be a thing of the past thanks to a team of European ...

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Hydrogen

Hydrogen (pronounced /ˈhaɪdrədʒən/) is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H2. With an atomic weight of 1.00794 u, hydrogen is the lightest element.

Hydrogen is the most abundant chemical element, constituting roughly 75% of the universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Elemental hydrogen is relatively rare on Earth. Industrial production is from hydrocarbons such as methane with most being used "captively" at the production site. The two largest uses are in fossil fuel processing (e.g., hydrocracking) and ammonia production mostly for the fertilizer market. Hydrogen may be produced from water by electrolysis at substantially greater cost than production from natural gas.

The most common isotope of hydrogen is protium (name rarely used, symbol H) with a single proton and no neutrons. In ionic compounds it can take a negative charge (an anion known as a hydride and written as H−), or as a positively-charged species H+. The latter cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds always occur as more complex species. Hydrogen forms compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules. As the only neutral atom with an analytic solution to the Schrödinger equation, the study of the energetics and bonding of the hydrogen atom played a key role in the development of quantum mechanics.

Hydrogen is important in metallurgy as it can embrittle many metals, complicating the design of pipelines and storage tanks. Hydrogen is highly soluble in many rare earth and transition metals and is soluble in both nanocrystalline and amorphous metals. Hydrogen solubility in metals is influenced by local distortions or impurities in the crystal lattice.

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