Formation of ions: Ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, resulting in a net positive or negative charge. Atoms with three or less electrons in their outer energy shell tend to lose electron to reach full outer shell for stability. Thus they form into a positively charged ions. (more protons than electrons) Atoms with 5 or more electrons tend to gain electrons to form a full outer shell for stability. Thus they turn into negatively charged ions. Having a full outer shell means stability to the atom. e.g. Na and Na+ Cl and Cl-

Quiz: Draw the structure of a carbon atom. What’s the difference between carbon-12 and carbon-14 atoms? Use the shorthand way (e.g. 2,8,8,2) for electronconfiguration, write the electron configuration for sulfur, nitrogen and potassium Why are Alkali metals so reactive? (group 1 elements , e.g. Li and Na and K etc). Why are noble gases so unreactive?( group 18 elements, e.g. Argon and krypton)

Notes and definitions: Atoms of nearly all elements bond (i.e. join together with other atoms, except the group 18 elements). Bonding can occur between atoms of the same element or different elements. Some elements occur naturally as particles called molecules, a molecule is an electrically neutral particle made up of two or more atoms bonded together. (can be of the same element) A compound is formed when atoms of different elements bind together. e.g. 2H2 + O2 = 2H2O

There are millions of compounds, but they almost all belong to the basic two types: Ionic compound: a substance formed by attraction between positive and negative ions. Examples such as salt. Covalent: substance formed by atoms sharing electrons. Examples include water and carbon dioxide.

How to work out name and formula of ionic compounds. An aluminium atom has the electron structure 2,8,3. It needs to lose 3 electrons to become stable.

An oxygen atom has the electron structure 2,6 An oxygen atom has the electron structure 2,6. It needs to gain 2 electrons in its outer shell to become stable.

2 x 3= 6 electrons from the aluminium and Oxygen To work out the number of ions of each element we need to balance the number of electrons being given and taken. 2 x 3= 6 electrons from the aluminium and 3 x 2 = 6 electrons to the oxygen 2- 3+ 2- 3+ 2- The formula is Al2O3

How to work out the formula of ionic compounds: Identify the positive and the negative ion. Work out their charge respectively. Note down how many ions you need to get a balanced charge. Write down the symbol for the atom (cation first, anion last) with the number of the atoms respectively e.g.Al2O3 How to work out names of the compounds. Identify the name of the cation. 2. Identify the name of the anion. 3. Anions change name with the suffix –ide. e.g. Aluminium oxide instead of aluminum oxygen.

Your task Find the

How to get from an atom to ion: Atomic Bonding How to get from an atom to ion: A normal atom is not positive or negative. This is because the number of protons (+ve) = the number of electrons (-ve). To find out the number of electrons a normal atom should have just look at its atomic number. An ‘normal’ atom will have this many electons. The electron shells of an normal atom fill up like this: 1st shell = max of 2 electrons 2nd shell = max of 8 electrons 3rd shell = max of 8 electrons A FULL outer shell is the most stable. Atoms will do almost anything to achieve full outer shells. Atoms will ‘give-away’ electrons in their outer shells to other atoms so that they achieve a full outer shell. Other atoms will readily ‘take’ electrons from other atoms so that they achieve a full outer shell of electrons. An atom that has given away or taken electrons will now be either positively or negatively charged. THESE ATOMS ARE NOW CALLED IONS. When different atoms join together they bond. Just like there is different types of glue, there are different types of bonding between atoms. All the information on this sheet is about a type of bonding called IONIC BONDING. Ionic (eye-on-ik) bonding means that the bonding happens between ions. Ions are just a scientific way of saying that an atom has more or fewer electrons than a normal atom of that element. Drawing atoms and ions Element Atom Ion Magnesium Chlorine Calcium Lithium A normal sodium atom Atomic number = 11 Number of protons =11 Number of electrons = 11 A sodium ion Atomic number = 11 Number of protons =11 Number of electrons = 10

Ionic Bonding One electron donated One electron accepted Ionic bonding only occurs between the ions of metals and non-metals. You need to know where to locate metals and non-metals. Properties of Ionic compounds Ionic compounds have strong bonds between particles. They generally have very high melting and boiling points. They also have good conduct electricity when molten or when dissolved in a water solution. While ionic inorganic compounds are solids at room temperature and usually form crystals. The ions produced by electron transfer attract each other by electrostatic attraction and this creates an ionic bond. Positive ions The metal atom donates an electron to the non metal atom. Because the metal atom has now got less electrons than protons, it has a positive charge overall. It is now a positively charged ion. Negative ions The non-metal atom receives an electron from the metal atom. Because the non-metal atom has now got more electrons than protons, it has a negative charge overall. It is now a negatively charged ion. What happens if there is more than one electron in the outer shell? If there is more than one electron in the outer shell of a metal then the metal will either have to donate its electrons to two non-metal atoms. Or it will have to donate electrons to an atom that has space for two electrons in the outer shell. What happens if there is space for more than one electron in the outer shell? This means that the non-metal will have to accept that number of electrons from one metal, OR it will have to accept electrons from more than one metal atom. One electron donated One electron accepted NaCl sodium chloride Two electrons donated Two electrons accepted MgO Magnesium oxide Metal Non-metal Two electrons donated One electron accepted by each non metal. CaCl2 Calcium chloride

Now try these: Lithium chloride Potassium bromide Magnesium Fluoride Potassium Chloride Magnesium chloride Calcium chloride Magnesium Oxide Magnesium chloride Calcium oxide