Ions - LeFonch

Ionic Bonding

The structural parts of substances are connected to each other by various bonds.
Examples of strong bonds are: Ionic bonds, metallic bonds and covalent bonds.
Ionic bonds are the strongest type of atomic bond.
Ionic bonds form between metals and nonmetals.
An ionic bond is an attraction between ions of different signs.
This is because negative and positive charges attract each other, causing the ions to form bonds.
Ionic bonds are held together by their strong opposite electrical charges and they the difference of electronegativity between atoms in the compound is greater than 1.7.
Keep in mind that ionic compounds have no partial charges.

Atoms always want to have full shields of electrons, and often give up or take electrons to make a full shield.
When a metal ion gives up an electron or electrons, it forms a positive ion.
Alkali metals and alkali earth metals are very prone to giving up electrons as they only have 1 or 2 valence electrons.
Some other metals like copper, gold and silver are very unreactive.
Normally the charge is balanced, however when giving up electrons it becomes positively charged.
Thus they become positive ions, which are called cations.
When a nonmetal receives an electron or electrons, it forms a negative ion, called an anion.
By taking negative electrons, the charge of an atom becomes negative, and thus unbalanced.
For example oxygen has 8 electrons, meaning only 1 of its shields are complete, whereas its second shield still needs 2 electrons to be a full octet.
This is why oxygen forms negative ions.
Halogens and chalcogens are the most prone to reacting.
Noble gases however practically never react as they have full valence shields.

Ionic charge can be inferred from the difference between protons and electrons.
For example, oxygen has 8 electrons and 8 protons. Thus when oxygen receives an additional 2 electrons, it has 10 electrons.
By calculating we can infer that: 8 - 10 = -2
This means that oxygen ions have a charge of negative 2.

Complete ionic compounds should have a total charge of 0, this is because the cations and anions in the compound should cancel each other out.
In the formula, cations are written first, and anions are written next.
The same applies to the name.
For example Na+ and Cl- form NaCl.
The relative number of ions is indicated by subscripts.
Names of metals in ionic compounds remain the same, (Magnesium, Sodium, Lithium, etc.) whereas nonmetals often have their names changed.
Such as Halogens, whose names end in "-ide" when in an ionic compound.
For example: Chlorine -> Chloride, Fluorine -> Fluoride, Sulphur -> Sulphide, Oxygen -> Oxide.
After the metal you might see (I), (II), (III) and so forth, which indicates the positive charge of the metal.

Due to their polarities, ionic compounds form an ionic lattice while in a solid state.
An ionic lattice is a three-dimensional, repeating structure that is formed by ionic bonding.
Ionic lattices have an alternating pattern, as the opposite sides of an ionic compound attract one another.
Ionic compounds have high melting points.
Ionic compounds are hard but brittle. This is because they are in a lattice, however the lattice can split on impact. This is because the ions of the same charge repel each other when the lattice is shifted.

An image showing the ionic lattice formed by sodium chloride, or NaCl.
Ionic compounds conduct electricity when dissolved in an aqueous solution, but not in a solid state.
As a solid, salts can't conduct electricity due to being tightly together and having a neutral charge. However in water they separate into their ions which are charged.

When water evaporates from the salt solution, some of the water molecules may remain in the ion lattice.
The water is called water of crystallization.
The water of crystallization is water in an ion lattice.
Crystal water is indicated in the formula of an ionic compound by a dot.
For example: CuSO₄.5H₂O
This would mean that the crystallized copper sulphate would have 5 water molecules per copper sulfate molecule. It is called copper sulphate pentahydrate, the prefix penta- meaning 5.

Atoms sizes can vary depending on their type of ion.
Cations are smaller than their non-ionic counterparts because they've given up an electron or multiple, reducing the size of their electron shields.
This is the opposite of anions, which have larger sizes than their neutral counterparts because they have additional electrons, which increase their size.
This effect scales, as the greater the positive charge of a cation, the smaller it's radius.
The opposite applies to anions as more negatively charged anions are larger.