# Question #aec3a

Dec 28, 2014

Not exactly. The atoms of elements can gain or lose electrons and become ions. Ions are charged particles that have gained or lost electrons. The atoms of elements can gain or lose electrons to form monatomic ions (made from a single atom of an element).

Atoms of elements that gain electrons develop a negative charge, such as the sulfide ion, ${\text{S}}^{2 -}$, which results when a sulfur atom gains two electrons; or the chloride ion, ${\text{Cl}}^{-}$, which results when a chlorine atom gains one electron.

The atoms of elements which lose electrons develop a positive charge, such as the aluminum ion, ${\text{Al}}^{3 +}$, which results when an aluminum atom loses three electrons; or the magnesium ion, ${\text{Mg}}^{2 +}$, which results when a magnesium atom loses two electrons.

There are also polyatomic ions, nearly all of which are negatively charged. They are formed when two or more atoms of different elements covalently bond, but end up with one or more extra electrons. One example, the sulfate ion, ${\text{SO"_4}}^{2 -}$, is composed of a central sulfur atom covalently bonded to four oxygen atoms, developing a negative two charge.

Dec 29, 2014

In some circumstances it is possible for elements to contain ions.

In metallic bonding we assume that the outer electrons are not localised to a particular atom but are free to move throughout the crystal

(Image from BBC)

So we have metal ions surrounded by a "sea" of negative electrons.

This model accounts for some of the physical properties of metals. They are malleable, ductile and are good conductors of electricity.

However the electrons are not lost as in ionic bonding so we cannot write a symbol such as $N {a}^{+}$.

At high voltages it is possible to ionise gases. A high energy electron can "knock off" an electron from a neutral molecule:

${O}_{2 \left(g\right)} + e \rightarrow {O}_{2 \left(g\right)}^{+} + 2 e$

This happens in electrical discharges.

At very high temperature plasma contains gaseous ions in equilibria with electrons. This is sometimes referred to as the "fourth state of matter".