Psychology & Psychiatry

Exactly how many senses do we really have?

While the notion that people have five basic human senses is often considered a universal truth and can be traced back to Aristotle's "De Anima" ("On the Soul"), many philosophers and neuroscientists are now debating whether ...

Medical research

Researchers reveal an added layer of nuance in our sense of smell

The delicate fragrance of jasmine is a delight to the senses. The sweet scent is popular in teas, perfumes and potpourri. But take a whiff of the concentrated essential oil, and the pleasant aroma becomes almost cloying. ...

Medical research

Awakening dormant cells to fight cancer

The advent of small-molecule targeted therapies, a decade ago, revolutionized the treatment of metastatic melanoma, provided that the tumors carry the mutations to respond to these treatments. However, despite a remarkable ...

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Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions and that have a unique and defined chemical structure. Chemical compounds consist of a fixed ratio of atoms that are held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be compound molecules held together by covalent bonds, salts held together by ionic bonds, metallic compounds held together by metallic bonds, or complexes held together by coordinate covalent bonds. Substances such as pure chemical elements and elemental molecules consisting of multiple atoms of a single element (such as H2, S8, etc.) are not considered chemical compounds.

Elements form compounds to become more stable. They become stable when they have the maximum number of possible electrons in their outermost energy level, which is normally two or eight valence electrons. This is the reason that noble gases do not frequently react: they already possess eight valence electrons (the exception being helium, which requires only two valence electrons to achieve stability).

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