Researchers explore architectural design of quantum computers

A recent study led by Princeton University researchers, in collaboration with University of Maryland and IBM, explored the architectural design of quantum computers (QC). In a paper presented at the 2019 ACM/IEEE International ...

The pH of calcium ions controls ion channel opening

Ion channels are pores in the membrane of cells or cell organelles. They allow positively or negatively charged particles, so-called ions, to be transported across the membrane. Biochemists at Johannes Gutenberg University ...

The similarities between a Van Gogh painting and a golf ball

On a molecular scale, there are surprising similarities between the outer shell of a golf ball and the white oil paint used by Van Gogh and his contemporaries. In both cases, the interactions between zinc ions and polymer ...

Expanding the temperature range of lithium-ion batteries

Electric cars struggle with extreme temperatures, mainly because of impacts on the electrolyte solutions in their lithium-ion batteries. Now, researchers have developed new electrolytes containing multiple additives that ...


An ion is an atom or molecule where the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge.

Since protons are positively charged and electrons are negatively charged, if there are more electrons than protons, the atom or molecule will be negatively charged. This is called an anion (pronounced /ˈænaɪən/; an-eye-on), from the Greek ἀνά (ana), meaning 'up'.

Conversely, if there are more protons than electrons, the atom or molecule will be positively charged. This is called a cation (pronounced /ˈkætaɪən/; cat-eye-on), from the Greek κατά (kata), meaning 'down'.

An ion consisting of a single atom is called a monatomic ion. If it consists of two or more atoms, it is called a polyatomic ion. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions.

When writing the chemical formula for an ion, its charge is written as a superscript '+' or '−' following a number indicating the difference between the number of protons and the number of electrons. The number is omitted if it is equal to 1. For example, the sodium cation is written as Na+, the '+' indicating that it has one less electron than it has protons. The sulfate anion is written as SO42−, the '2−' indicating that it has two more electrons than it has protons.

If an ion contains unpaired electrons, it is called a radical ion. Just like neutral radicals, radical ions are very reactive.

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