Introduction and Ionic Bonding

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Introduction:

bonding = electrostatic attraction between two oppositely charged species

3 types of bonding: ionic, covalent, metallic

Difference between atoms and ions:

- atoms are uncharged

- number of protons in an atom is the same as the number of electrons

- if an atom gains or loses an electron, it will become electrically charged

Metal atoms and hydrogen atoms form positive ions

- sodium atom loses one electron to form a positively charged sodium ion

Non-metallic elements form negative ions

- do this by gaining electrons

- chlorine atom gains one electron to become a chloride ion, Cl-

Negative ions: anions

Positive ions: cations

Polyatomic ions:

- hydroxide ion OH-

- nitrate ion NO3-

- sulphate ion SO42-

Any atom becomes an ion if it loses or gains electrons

ion is a charged particle

- it is charged because it contains an unequal number of protons and electrons

Reaction between two atoms (sodium and chlorine)

sodium atom can lose one electron

chlorine atom can gain one

TO OBTAIN FULL OUTER SHELLS

when a sodium atom and a chlorine atom react together:

- the sodium atoms loses one electrons

- the chlorine atom gains one electron (the one sodium lost)

Metals (left-hand side of the periodic table) have only a few electrons in their outer shell = easier for them to form ions by losing electrons

Non-metal atoms have almost full outer shells = easiest for them to form ions by gaining electrons

Ions formed by metals will have a positive charfe because there are less electrons than protons present in the ion

Ions formed by non-metals will have a negative charge bacause there are more electrons than protons

A

According to the valencies of the different atoms, the number of ions in a reaction will change

Sodium Chloride

when sodium reacts with chlorine, billions of sodium and chloride ions form = attracted to each other

Ions do not stay in pairs --> cluster together

held together by strong ionic bonds

each ions forms six bonds

equal numbers of each atom

lattice structure

regular arrangement of alternating positive and negative ions

Ionic compounds are always solids at room temperatures

- high melting and boiling points

Empirical formula: ratio of number of atoms in each compound in a reaction

Introduction to Ions

Ionic Bonding

Crystals

Valencies and Formulas