Ionic Bonding Ions are charged atoms. This is when an atom has gained or lost an electron. An atom’s ion is based on their outer electron shell. The number of electrons in the outer shell dictates whether it will gain or loose electrons. Positive ions are called cations. Negative ions are called anions. Atoms will form Ionic Compounds e.g., sodium chloride (table salt) when they combine their electrons with another atom. In ionic compounds, metal ions combine with non-metal ions.

Atoms have a hard time to gain or lose 3 or 4 electrons. Common Ions You Really Should Know 1+ ions 2+ ions 3+ ions 4+/4- ions 3- ions 2- ions 1- ions Li+ Mg2+ Al3+ Very Rare Fairly O2- (oxide) F- (fluoride) Na+ Ca2+ Fe3+ (Iron(III) S2- (sulphide) Cl- (chloride) K+ Ba2+ Cr3+ Br-(bromide) Cu+ Cu2+ I-(iodide) Ag+ Fe2+ (Iron(II) NO3-(nitrate) H+ Zn2+ SO42- (sulphate) OH-(hydroxide) NH4+ (Ammonium) Pb2+ CO32- (carbonate) HCO3-(hydrogencarbonate) These atoms lose one electron to form 1+ ions. (NH4+ isn’t an atom) These atoms lose two electrons to form 2+ ions. These atoms lose three electrons to form 3+ ions. Atoms have a hard time to gain or lose 3 or 4 electrons. These atoms / molecules gain two electrons to form 2- ions These atoms / molecules gain one electrons to form 1- ions

Ionic Compounds - examples So: Ionic bonding occurs basically by gaining or losing electrons.

Ionic Bonding Video – Sad Electrons.

Covalent Bonding Covalent bonding occurs when two or more atoms share electrons and a molecule is formed. A chemical bond formed by the sharing of electrons creates a covalent compound. Covalent bonding occurs between two or more non-metals, whereas, ionic bonding occurs between metals and non-metals. Molecules can be made of more than one type of atom, or made of atoms of the same element.

For example: Hydrogen atoms have just one electron For example: Hydrogen atoms have just one electron. They only need more to complete the first shell. So hydrogen prefer to share with another atom, sometimes another hydrogen, to form hydrogen gas (H2) one H H X This forms a single covalent bond!

Some atoms have more space that need to be filled, such as Oxygen Some atoms have more space that need to be filled, such as Oxygen. Oxygen is happy to share with more than one atom. H2O is now formed and all atoms are have a completed shell through sharing electrons. O H H Some atoms such as Hydrogen only have one electron to share so they can easily join in on the sharing. But Hydrogen needs to bring a friend in order to make the Oxygen feel complete.

Common Covalent Bonds

Electronic Configuration Symbol Electronic Configuration Electron Dot Diagram H C O S Cl N F H 1 C 2,4 O 2,6 S 2,8,6 Cl 2,8,7 N 2,5 F 2,7

Covalent Bond – Angry bonds

Reactivity The reactivity of metals depends on how easily the able to give up their outer shell electron. An element with only one electron to give from its outer shell is more reactive than those with two electrons to give. Metals react with acids which can be used to show reactivity. This reaction separates / displaces the hydrogen from the acid to produce hydrogen gas. The equation is: metal + hydrochloric acid ---> salt + hydrogen gas. This is call displacement reactions.