It’s All A Bit Ionic! http://twobluefish.blogspot.com/2011/06/confusion.html
Today’s Lesson • The wonders of Compounds • Ions are what? • Ionic Bonding • Working Out Charges Worksheet
Catatonic Compounds • So what’s the difference between elements and compounds? • This is what we will now be learning about. We’ll be seeing how different atoms bond and what properties then might have because of that. • For example, does anyone know why most non-metals when bonded have a low MP and BP.
Elements & Compounds • Elements are one type of atom by themselves which is pure. • A compound is two or more atoms together. • Noble Gases normally don’t form compounds • Atoms like to have full outer electron shells. • If there is 1, 2 or 3 electrons in outer shell, it is more likely to lose those electrons • If there is 5, 6 or 7 electrons in outer shell, it’s more likely to gain electrons.
Ions • Ions are atoms that have gained or lost electrons to have a full outer shell • Sodium loses one electron so it now has a positive charge. So we write it as Na+ (the plus is normally in the same place as a power in maths). • So, if you lose 3 electrons it will be 3+. • If you gain 3 electrons it will be 3-.
Some Hints • When you write the charge (+ or -) of an ion, you write it in the same place as a power. Eg Na+. • When you write how many atoms you have, you write it down on the bottom right. Eg O2. • When making a compound, it is normally stable. This means there is the same number of electrons as there are protons.
Ions • Atoms like to have full outer electron shells. As such, they tend to gain or lose electrons. • Atoms with 1,2 or 3 electrons in the outer shell (apart from Hydrogen) tend to lose electrons and become a positive ion (positive valency) as they have more protons than electrons. • Atoms with 5, 6 or 7 electrons in the outer shell tend to gain electrons and become a negative ion (negative valency) as they have less protons than neutrons.
Ionic Bonds • When an anion (negative ion) and cation (positive ion) are close, they can bond or join together. • For example in Sodium (Na+) and Chlorine (Cl-), the Sodium will transfer one electron to Chlorine. • Both atoms are now stable and have bonded together.
A Special Bond • The total charge in an ionic bond is normally 0 • 2 Chlorines (Cl-) can bond with one Magnesium (Mg 2+). • An ionic compound occurs when an anion and cation bond together. • When they bond together – think of them as little magnets. + and – want to go next to one another as 2 of the same charges repel.
Naming anions in Ionic Equations • By itself, Chlorine is called Chlorine. • As a compound, it’s called Chloride. • Anions (atoms with more electrons than protons) change their name with ide on the end. • Examples are: • Oxygen = Oxide • Iodine - Iodide
Questions • Complete the worksheet given to you. If you finish early, answer the questions below: • 1) What is an Ion? • 2) How is an Ion different to am atom? Explain. • 3) What are cations and anions? Give examples. • 4) Explain how you can work out the charge of an ion. Give an example for a positive and negative charge. • 5) Are group 1 elements normally cations or anions? Explain. • 6) Are group 7 elements (halogens( normally cations or anions? Explain. • 7) What is the difference between elements and compounds? Give 2 examples of an element and a compound and explain how they are different.