1. Chemists believe that many chemical compounds contain ions Common Properties of these compounds: ◦ High melting point (ex: salt melt at 800*C)

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Chemists believe that many chemical compounds contain ions

Common Properties of these compounds:◦High melting point (ex: salt melt at 800*C)

◦Tightly packed structure (Crystal Lattice)

◦As a solid does not conduct but when melted is a good conductor

◦Pure water does not conduct electricity but when the cmpd is dissolved in water, the solution conducts electricity.

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The arrangement of sodium ions

(Na+) and chloride ions (Cl-) in the ionic compound sodium chloride.

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Solid sodium chloride highly magnified.

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(a) Pure water does not conduct a current; (b) Water containing a dissolved salt conducts electricity

A substance containing ions that can move can conduct electric current

Dissolving salt (NaCl) causes ions to be dispersed in the water move freely

Some substances dissolve in water to form a solution that conducts well - these are called electrolytes

When dissolved in water, electrolyte compounds break up into component ions

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Ionic compounds – a compounds formed between a metal and a nonmetal

An ionic compounds must contain a net charge of ZERO

Must be composed of anions AND cations

Total charge of cations + total charge of anions = Zero net

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Na+ and Cl- NaClCharge (+1) and (-1) net 0

Mg2+ and Cl- Cation (+2) and Anion (-1)Need 2 anions (-2) for Net 0 charge

Lithium and Nitrogen8

Chlorine and calcium

Sodium and sulfur

Calcium and phosphorus

Oxygen and barium

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ions that have a positive charge are called cations◦form when an atom loses electrons

ions that have a negative charge are called anions ◦form when an atom gains electrons

ions with opposite charges attract ◦therefore cations and anions attract each

other moving ions conduct electricity compound must have no total charge, therefore

we must balance the numbers of cations and anions in a compound to get 0 total charge

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