Types of Compounds Sec. 3.2: Ionic compounds

Ion comes from the Greek word meaning “to wander” Ionic compounds are… What is an ion? Ion comes from the Greek word meaning “to wander” Ions are ELEMENTS whose electrons have gone traveling, and when they meet up with an opposite ion, the WHOLE atom comes with! Chemical compounds that consist of charged ions with opposite charges.

We use superscripts to show the ion charge. A superscript is … Some ions have a positive charge (+) and some have a negative charge (-). Metals are (+) Non-metals are (-) We use superscripts to show the ion charge. A superscript is … Ex. Na+, Sn2+, O2-, F- A tiny letter/ number above the term, like an exponent.

Ion Charges 1+ 2+ 3+ 3- 2- 1- Multiple charges…check the box.

In order to write an ionic formula, you need to know the ion charge. This is because ionic compounds are always neutral… there are the same numbers of positives as negatives Ex: Water. Ion = H+ and O 2-. There needs to be 2 H+ so the charges can equal out. H+, H+ , O 2- We write this as H20(l)

There are three simple steps to follow: Turn to page 147 and paraphrase each step in the boxes below.

Step 1 Write each ion with its charge *Remember: Certain columns on the periodic table are always the same, and some have more than one choice.

Step 2 Figure out how many of each you need to make the charges balance. The best way is to do a switch-er-oo between the number of atoms and the opposite ion’s charge. Ca2+ and Br – 1 Ca and 2 Br Ca2+, Br – ,Br –

Step 3 Write the formula using subscripts to show how many of each atom you need AND the state Ca2+ and Br – 1 Ca and 2 Br Ca2+, Br – ,Br – CaBr2 (s) * Ionic compounds are always solid (s)

Multiple charges… These are called polyatomic ions. In order to know Poly means “multiple” or “more than one”. In order to know which of the ion charges you need the formula will have a roman numeral in it. Cr2+ is written chromium (II) Co3+ is written cobalt (III)

Do C & R Questions 1-8 on page 149