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IonsAn ion is an atom or group of atoms that have a net electrical charge. An ion is formed when electrons or protons are gained or lost by an atom.
There are two types of ions: Cations and Anions.
Cations :A positively charged ion is known as cations. A cation is formed by the loss of one or more electrons by an atom.
Anions: A negatively charged ion is known as Anion. An anion is formed by the gain of one or more electrons by an atom.
Ionic Compounds The compounds which are made up of
ions are known as ionic compounds. In an ionic compound, the positively
charged ions and negatively charged ions are held together by the strong electrostatic forces of attraction.
The forces which hold the ions together in an ionic compound are known as ionic bonds and electrovalent bonds.
Since an ionic compound consists of an equal number of positive ions and negative ions, so overall charge of an ionic compound is zero.
Example: Sodium chloride- NaCl Potassium Chloride- KCl
+ =
Na Cl NaCl
In general, a cation will react with an anion to acquire a full valence shellIn general, a cation will react with an anion to acquire a full valence shell
Some Ionic CompoundsName Formula Ions present
1. Sodium Chloride NaCl Na+ and Cl-
2.Potassiun Chloride
KCl K+ and Cl-
3.Ammonium Chloride
NH4Cl NH4+ and Cl-
4.Magnesium Chloride
MgCl2 Mg2+ and Cl-
5. Calcium Chloride CaCl2 Ca2+ and Cl-
6. Magnesium Oxide
MgO Mg2+ and O2-
7. Calcium Oxide CaO Ca2+ and O2-
8.Aluminium Oxide Al2O3 Al3+ and O2-
9.Sodium Hydroxide
NaOH Na+ and OH-
10.Copper Sulphate CuSO4 Cu2+ and SO42-
11.Calcium Nitrate Ca(NO3)2 Ca2+ and NO3-
Note: Ionic compounds are made up of a metal and a non-metal(except ammonium chloride which is made up of only non-metals.
Ionic Bond
The attraction between the cation and the anion is known as an ionic bond. This bond is what holds the ionic compound together.
The attraction between the cation and the anion is known as an ionic bond. This bond is what holds the ionic compound together.
Formula Unit of Ionic Compounds
The simplest combination of ions that produces an electrically neutral unit, is called a ‘Formula Unit’ of ionic compound.
The ‘formula unit’ of an ionic compound can be thought of as the smallest unit that compound, it is the equivalent of a ‘molecule’ of the compound.
Formula Mass
Formula mass is the sum of the atomic masses of the atoms (or ions) represented by its formula.
In order to calculate the formula mass of an ionic compound, we should know the formula of the ionic compound as well as the atomic masses of all the atoms (or ions) present in the formula.
Example
To calculate the formula mass of potassium carbonate (K2CO3):
Atomic masses: K= 39u ; C= 12u ; 0= 16uFormula mass of K2CO3
=
Mass of 2 K atoms
+Mass of one C atom
+Mass of 3 O atoms
= 2*39 + 12 + 3*16
= 78 + 12 + 48
= 138u
Thus, the formula mass of potassium carbonate is 138u.
Properties of Ionic Compound
At room temperature, most are hard, brittle solids that can be crushed.
Ionic compounds form crystals that have an alternating arrangement of positively charged ions and negatively charged ions, so that when they break their edges are well-defined.
Properties of Ionic Compound
Properties of Ionic Compound
In an ionic crystal, every ion is attracted to every other ion in the crystal. As a result, ionic crystals have very high melting pointsex.) NaCl melts at 800oC
In an ionic crystal, every ion is attracted to every other ion in the crystal. As a result, ionic crystals have very high melting pointsex.) NaCl melts at 800oC
Properties of Ionic Compound
When an ionic compound dissolves in water, the crystal structure breaks down and the ions become free to move.