ionic chemical formulae. & balancing equations

Ions

• when elements gain lose electrons, they are known as ions

• Group 1,2,3 elements (metals)

→ tend to lose electrons

→ gain positive charge of +1,+2,+3

• group 15,16,17 elements (non-metal)

→ tend to gain electrons

→ Gain a negative charge of -1,-2,-3

• Positive ions are known as cation

• Negative ions are known anion

• Ionic compounds form through ionic bonding between 1 metal cation and 1 non-metal anion

Ionic bonds

• if electrons between elements are given and recieved then ionic bonds are formed

Write the balanced ionic equation

1. Draft the equation

2. Balance the positive and the negative charges so the outcome is neutral, add the coefficient

3. A) swap the superscript(top) numbers between the two ions

B) drop them to the superscript (bottom) position

C) drop the charges (if the same numbers remain on both sides, remove them (eg: Mg2Os becomes MgO))

Polyatomic ions when balancing equations

• polyatomic ions = ions that contain more than 1 atom

• Treat them like a single ion when balancing equations

Chemical equation - acid-base reaction(neutralisation )

• hydrochloric acid + sodium hydroxide → sodium chloride + water

Chemical reactions - acid-metal reaction

• metal + acid → ionic slat + hydrogen gas (H2)

Chemical reactions - combustion reaction (burning in oxygen)

• hydrocarbon + oxygen → carbon dioxide + water

Chemical reactions - precipitation reaction

Solid formed from 2 solutions

Steps for balancing chemical equations

1. Determine the reactants and products and write a word

2. Determine the chemical formulae

3. Write down the equation

4. Balance the numbers of atoms

5. Include the states