Ionic Compound | What Is An Ionic Compound
In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ions called anions. These can be simple ions such as the sodium (Na+) and chloride (Cl−) in sodium chloride, or polyatomic species such as the ammonium (NH+4) and carbonate (CO2−3) ions in ammonium carbonate. Individual ions within an ionic compound usually have multiple nearest neighbours, so are not considered to be part of molecules, but instead part of a continuous three-dimensional network, usually in a crystalline structure.
Ionic compounds containing hydrogen ions (H+) are classified as acids, and those containing basic ions hydroxide (OH−) or oxide (O2−) are classified as bases. Ionic compounds without these ions are also known as salts and can be formed by acid–base reactions. Ionic compounds can also be produced from their constituent ions by evaporation of their solvent, precipitation, freezing, a solid-state reaction, or the electron transfer reaction of reactive metals with reactive non-metals, such as halogen gases.
Ionic compounds typically have high melting and boiling points, and are hard and brittle. As solids they are almost always electrically insulating, but when melted or dissolved they become highly conductive, because the ions are mobilized.
Ionic Compounds Are Balanced
Table salt is an example of an ionic compound. Sodium and chlorine ions come together to form sodium chloride, or NaCl. The sodium atom in this compound loses an electron to become Na+, while the chlorine atom gains an electron to become Cl-. Together, they form a neutral compound because the ions balance each other out. This is true for all ionic compounds – the positive and negative charges must be in balance.
Potassium oxide, or K2O, is another example of an ionic compound. You may have noticed that unlike the sodium chloride example, which has one sodium ion for each chlorine ion, this time there are two potassium atoms for each oxygen. This is because the charges have to be balanced for the ionic compound. All you have to do to determine how many of each ion will be in the compound is take a quick look at the periodic table.
Let’s start with our table salt, the sodium chloride. Sodium is in the first column of the periodic table, so it will lose one electron. Chlorine is in the second-to-last column, so it will gain one electron. Each atom in this ionic compound will lose or gain one electron, so they can pair up in a one-to-one ratio.
Bonding in Ionic Compounds
In its purest form, ionic bonding is not directional. It can be regarded as simple positive-negative Coulombic attraction between point charges. This is different from covalent bonding, in which electrons are shared by atoms, forming directional bonds.
However, absolutely pure ionic bonding does not exist. There is always at least a small degree of covalent bonding character in ionic compounds.
Ionic Compound Examples
Q: State whether the following statement is true or false. Sodium Chloride has a higher melting point than Magnesium Oxide. Justify your answer.
Ans. The following statement is True. Magnesium Oxide (MgO) has a higher melting point than Sodium Chloride (NaCl) which is around 2,800 degrees Celcius. This is because its Mg2+ and O2- ions have a greater number of charges, and so form stronger ionic bonds, than the Na+ and Cl- ions in Sodium Chloride. Because it stays solid at such high temperatures, magnesium oxide remains non-conductive and is used for high – temperature electrical insulation.
Ionic Compound Formula
In an ionic compound, such as common salt, NaCl, or magnesia MgO, the formula tells us the correct ratio of elements present, but it does not specify the unit. Ionic compounds exist as giant crystal lattices.Each crystal contains an unspecified number of ions: the numbers are enormous: even a 0.5 gram crystal of sodium chloride contains about 1 x 1022 ions.The structures of crystals can be understood in terms of their repeating units – unit cells: these can be determined by X-ray diffraction measurements.
Ionic Compound Properties
- Ionic Compounds have high boiling and melting points as they’re very strong and require a lot of energy to break.
- The electrostatic forces of attraction between oppositely charged ions lead to the formation of ions.
- Ionic compounds form crystals.
- These compounds are brittle and break into small pieces easily.
- Electrovalent compounds usually dissolve in water and are insoluble in solvents like oil, petrol, kerosene, etc.
- Ionic compounds do not conduct electricity in a solid state but they do conduct electricity in the molten state.
- In comparison to molecular compounds, ionic compounds have higher enthalpies of fusion and vaporization.
Binary Ionic Compound
A binary ionic compound is composed of ions of two different elements – one of which is a metal, and the other a nonmetal. For example, iron(III) iodide, FeI3, is composed of iron ions, Fe3+ (elemental iron is a metal), and iodide ions, I–(elemental iodine is a nonmetal).