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what is ions?

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4 Answers

Ions have a charge

Example:  NaCl is a molecule that is formed by two entities that have charges, ions! 

In this example, Na has a +1 charge (cation) & Cl has a -1 charge (anion). 

NaCl is an ionic compound! 

All elements listed in the 1st and 2nd column, known as groups 1 & 2, on the periodic table have +1 and +2 charges, respectively. 

All element listed in the 6th and 7th column, known as groups 6 & 7, on the periodic table have -2 and -1 charges, respectively. 

The relative charges for each ion help attract the number of ions in a particular molecule. 

For example:  CaCl2. 

The Ca ion has a charge of +2. 

It attracts 2 Cl ions because Cl has a charge of -1

 

An ion is either an atom or a molecule that is not in the ground state (having zero charge).

A positive ion is called a cation and has had at least one electron removed from it. (In some cases a proton has been added)

A negative ion is called an anion and has had at least one electron added to it. (In some cases a proton has been removed)

Ions are typically formed due to the differences in electronegativity of the nuclei.

For example, if you add Sodium metal to water, positive sodium ions and negative hydroxide ions are formed. In this case the loss (and addition) of electrons are called a "redox" reaction where reduction (addition of an electron) and oxidation (removal of an electron) are coupled together to form aqueous NaOH and H2 gas.

Charge balance dictates that the net charge of the universe is equal to zero and that for every positive ion formed there is an equal and opposite negative ion to balance it out. In other words if you take away to make a negative charge, you leave a positive charge.

Hopefully I haven't convoluted my answer but in simplest terms, an ion is an atom or molecule that possesses some amount of charge and is coupled to an ion of opposite charge.

Comments

Best not to use "ground state" for neutral vs. charged species. For chemistry, this refers to species related by a difference in energy level of an electron, or electrons, either in local or molecular orbitals; the lowest possible energy state is "ground state", and the upper, an "excited state" (there's lots of spectroscopic terminology associated, too).

And then, there are also molecules that have transferred a proton from one place to another *on the same molecule*, resulting in one site that is positively charged (typically an RNH3+) and another that is negatively charged (perhaps an RCOO- or an RSO3-) at the same time; they are called "zwitterions".

The correct way to state this question is "What are ions?"  Ions are atoms of an element with a positive or negative charge. To understand what ions are you need to understand how they get to be ions. It has to do with subatomic particles. Atoms are made up of protons, neutrons and electrons (subatomic particles) . Protons are positive, neutrons are neutral and electrons are negative. Each element is identified by the number of protons it has in its nucleus or center. This is its atomic number. For example, Oxygen's atomic number or place on the periodic table is 8 so it has 8 protons. Neutrons exist in the nucleus with the protons, but have no effect here because they are neutral. Electrons are floating around the nucleus in shells or levels. When an atom is not reacting with any other element the number of electrons balances the number of protons. So oxygen also has 8 electrons when it is not reacting. But, when it is reacting, as things often do in the real world, the electrons in the outer shell may be exchanged or shared with other elements. Only the outer shell electrons can do this because they are on the outer boundaries of the atom. When an atom gives away or loses an electron to another atom it becomes a positive ion or cation because there are now more protons than electrons. When it gains an electron from another atom it becomes a negative ion or anion because it now has more electrons than protons. How these electrons are configured in the outer shell and their ability to bond in different ways is the basis for chemical reactions. So, understanding ions is important to understanding chemical reactions.

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