IONIC COMPOUNDS WHATS AN ION Recall an electron

IONIC COMPOUNDS

WHAT’S AN ION?

Recall: an electron is a negatively charged particle! WHAT’S AN ION? • An ion is an atom or group of atoms that has become electrically charged through the loss or gain of electrons

SOME EXAMPLES OF ION CHARGES FOR VARIOUS ELEMENTS Element Hydrogen Lithium Nitrogen Oxygen Iron Copper Ion Charge Ion Notation H+ N 3 Fe 2+ or Fe 3+

WHAT’S AN ION? • A positive charge (1+, 2+, etc. ) To remember: CATS have means the atom has lost electrons PAWS, so cations are paws itively • We call it a “cation” charged

WHAT’S AN ION? • A negative charge (1 , 2 , etc. ) means the atom has gained electrons • We call it an “anion”

WHAT’S AN ION? • Summary More protons than electrons Protons = Electrons More electrons than protons

USING ION CHARGES AND CHEMICAL NAMES TO WRITE FORMULAS You can find an element’s charge by looking at the periodic table

EXAMPLE: CALCIUM AND CHLORINE STEP 1 Write the metal’s symbol with its ion charge. Then write the non metal’s symbol with its charge. 2+ Ca 1 Cl

EXAMPLE: CALCIUM AND CHLORINE STEP 2 Balance the ion charges. The positive ion charge must balance the negative ion charge (must sum to zero) Ca 2+ 2+ 2 Cl 1 The charges are balanced

EXAMPLE: CALCIUM AND CHLORINE STEP 3 Write the formula. Indicate how many atoms of each element there are using subscripts. Ca. Cl 2

YOU TRY! What is the chemical formula for the compound that forms from aluminum and fluorine? 1. 2. 3. 4. Determine chemical symbols Determine chemical charges Balance charges Write formula using subscripts

Git yer markers ready… What is the chemical formula of the compound formed between calcium and oxygen?

PRACTISE