This document discusses several chemistry concepts including isotopes, ions, and bonding. It defines isotopes as atoms of the same element with different numbers of neutrons but the same number of protons. Metals form cations by losing electrons while non-metals form anions by gaining electrons. There are two main types of bonding - ionic bonding between metals and non-metals formed by electrovalent bonds, and covalent bonding where non-metals share electrons. Chemical equations are used to represent chemical reactions and must be balanced.

1. Solubility and chemical equationsChapter Two

2. IsotopesIsotopes are atoms of the same element with the same number of protons but different number of neutrons.Isotopes have the same chemical properties as the electrons in isotopes are similar.Isotopes have slightly different physical properties due to differing relative masses.Example : Chlorine-35 and Chlorine-37

3. Cations and AnionsMetals from cations (positively charged ions) by losing electrons.Formation of cations : (Sodium) Na [Na] +Non-metals form anions (negatively charged ions) by gaining electrons.Formation of anions : (Oxygen) O [O] 2-

4. Molecules of elementsHere are a few common examplesHydrogen – H2Oxygen – O2Nitrogen – N2Chlorine – Cl2Bromine – Br2Phosphorus – P 4Sulphur – S 8

5. Polyatomic IonsPolyatomic ions are ions of grouped atomsHere are a few common examplesNitrate – NO3-Hydroxide – OH -Carbonate – CO32-Sulphate – SO42-Phosphate – PO43-Ammonia – NH3+Ammonium – NH4+

6. Ionic bondingIonic bonding between metals and non-metals is formed by electrovalent bonds.Examples :Na ++ Cl-[Na]++ [Cl]-Na ClMg 2++ Cl -[Mg] 2++ 2[Cl]- Mg Cl2Notice that the ions of both elements are swapped to become the chemical formula of the compound.This also applies to covalent compounds.

7. Covalent bondingNon-metals share electrons to create covalent bonding between one other.Examples :H-+ O2-[H]1+1=2 [O]6+2=8 H2OC4-+ H-[C]4+4=8 [H]1+1=2 CH4Although the formation of the chemical formula is the same as ionic compounds, the method of bonding is different.Both atoms gain electrons through sharing.

8. Chemical EquationsLithium burns in bromine to form lithium bromide.Li + Br Li BrNickel (II) carbonate decomposes on heating to form nickel (II) oxide and carbon dioxide.Ni CO3Ni O + CO Sometimes, chemical equations have to balanced to be complete.

9. Balancing EquationsNitrogen reacts with oxygen to form nitrogen monoxide.N2+ O2 2 NOSilver nitrate decomposes on heating to form silver, nitrogen dioxide and oxygen.2 AgNO32 Ag + 2 NO2+ O2Iron (III) sulphate reacts with sodium hydroxide to form rubidium nitrite and oxygen.Fe (SO4)3+ 6 Na OH 2 Fe (OH) 3+ 3 Na2 SO4

10. Soluble elementsDefinite solubilityAmmonium saltsSodium saltsPotassium saltsNitrates

11. Soluble elementsSolubility with exceptionsChlorides except Lead (II) and SilverSulphates except Barium, Calcium and Lead (II)

12. Insoluble saltsCarbonatesexcept other soluble saltsHydroxideexcept other soluble salts and CalciumOxidesexcept other soluble salts and Calcium