Atoms and Reactions

Atoms and Reactions

1. ATOMIC STRUCTURE

   • The nucleus is made from Protons and Neutrons
   • Electrons orbit the nucleus in shells
   • Most of the atom is empty space
   • PROTONS have a relative mass of 1 and a relative charge of 1+
   • NEUTRONS have a relative mass of 1 and a relative charge of 0
   • ELECTRONS have a relative mass of 1/2000 and a relative charge of 1-
   • ISOTOPES
     • Different mass
     • Same number of protons and electrons (therefore same charge)
     • Different amount of neutrons
     • Means 'at the same place' in greek
     • 'Atoms of the same element with different numbers of neutrons and different masses'
     • CARBON ISOTOPES
       • Each isotope of carbon has 6 protons
       • There is 3 isotopes of carbon
       • Overall charge is zero
       • Different masses due to increase/decrease in neutrons
       • The reactivity of all three carbon isotopes is th same as only electrons are involved in chemical reactivities
   • ATOMIC (PROTON) NUMBER is the number of protons in the nucleus of an atom
   • MASS (NUCLEON) NUMBER is the number of protons and neutrons in the nucleus.
   • ION STRUCTURE
     • A positivly or negativly charged atom/group of atoms
       • Caused by the loss or gain of electrons

2. ATOMIC MASSES

   • Atoms are meausured in unified atomic mass units (u).
   • CARBON 12 is the standard measurment for realtivie atomic mass
   • An atom of carbon 12 is 12 u, thus 1 u is equal to 1/12th of carbon 12.
   • RELATIVE ATOMIC MASS is weighed mean mass of of an atom of an element compared to 1/12th of carbon 12
     • (massXpercentage)+(massXpercentage)/100
   • RELATIVE ISOTOPIC MASS is the mass of an atom of an isotope compared to 1/12th of carbon 12

3. MOLES

   • Number of Moles = Mass/Molar Mass
   • Number of Moles = Concentration X Volume (Dm3)
   • Number of Moles = Volume (Dm3)/ 24
   • The amount of atoms is based on a standard count of atoms called the ADVOGADROs CONSTANT, the number of atoms in 1 mole of carbon 12 isotope
   • 6.02 x10(23)
   • A MOLE is defined as the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon 12
   • Molar Mass=Atomic Mass
   • AVAGADROs LAW VOLUME
     • If there is an equal volume of gases at the same tempreture and pressure it has an equal number of molecules
       • 1 mole of gas occupies 24Dm3 (24000cm3)
       • Molar volume = volume per mole of gaseous molecules
   • MOLES AND SOLUTIONS
     • In a solution there is a solute dissolved in a slovent, concentration tells you how many moles of solute is dissolved in a Dm3 0f solvent
     • Mol Dm-3
     • EG: 2 MolDm-3 is qual to 2 moles of substance per Dm3
     • A standard solution is one that is known. to create a standard solution do the following ...
       • *consider volume of solution required *work out the amount in moles of solute needed *convert this into mass (g)
       • 1) weigh out solute 2) completley dissolve the solute in water in a beaker, transfer into a volumetric flask and rinse the beaker repeatedly adding it to the flask 3) add water to the flask, but dont fill it all the way 4)carfully add drop by drop water up to the bottom of the meniscus of the graduation mark
     • Meniscus
     • CONCENTRATED is a large amount of solute per Dm3 usually greater than 10MolDm3
     • DILUTE is a small amount of solute per Dm3

4. TYPES OF FORMULA

   • EMPIRICAL FORMULA is the simplest whole number ratio of atoms in each element present in a compound
     • Find molar ratio and divide each one by the smallest mole
     • usefull for giant compounds
   • MOLECULAR FORMULA is the number of atoms in each element present in a molecule
     • usefull for simple compounds
   • Changing from EMPIRICAL TO MOLECULAR FORMULA you divide the relative molecular mass (given to us) by the empirical formula mass and then times the emerical by whatever number you find.

5. CHEMICAL EQUATIONS

   • Chemical reactions DO NOT create or destroy atoms, they merly rearange the combinations of atoms
   • Reactants --> Products
   • A chemical equation is a symbol of a chemical reaction where you can show various chemical species in different ways
     • A SPECIES is a particle that takes part in a chemical reaction, can be either an atom, ion, molecule or even an electron
   • A GIANT STRUCTURE is formed when many atoms or ions bond together usually to form a crystaline structure or lattice. eg: ionic compounds like NaCl and giant covalents like SiO2
     • All metals are giant structures
     • Some non-metals are giant structure eg:C, Si and B
   • STATE SYMBOLS: (s) solid (l) liquid (g) gas (aq) aqueous

6. STOICHIOMETRY

   • The molar relationship between the relative quantities of substances taking part in a reaction.
   • You need a balanced equation, this tells you the reacting quantities needed to prepare a required quantity of product and the quantities of products formed by reacting together the known quantities of reactants.
   • RATIO

7. ACIDS AND BASES

   • ACIDS are a species that is a proton donor. All acids contain hydrogen and when added to water the H+ions are released.
     • EXAMPLES: Sulfuric Acid (H2SO4) Hydrochloric Acid (HCL) Nitric Acid (HNO3)
       • Weaker Nsturally ocuring acids include Ethanoic Acid (CH3COOH) Methanoic Acid (HCOOH) Citric Acid (C6H8O7)
     • HCl(g) + aq --> H+(aq) + Cl-(aq)
     • PH<7 when aq
   • BASES are a species that is a proton acceptor.
     • Accepts H+ Ions
     • Bases neutralise Acids
     • Common Bases are metal oxides and hydrxides, eg:MgO, CuO and NaOH, Mg(OH)2
     • Ammonia And Amines are also bases. NH3 and CH3NH2
   • Everyday Bases, *Magneium Hydroxide (Mg(OH)2 used in treating indegestion *CalciumHydroxide (Ca(OH02) lime used to treat acid soils
   • ALKALIS are a type of base thst dissolve in water forming hydroxide ions (OH-) aq
     • PH>7 when aq
     • Common Alkalis include... Sodium Hydroxide (NaOH) Potassium Hydroxide (KOH) Ammonia (NH3)
       • NaOH is used in paint strippers and oven cleaners
     • Very corrosive, more so than acids
       • For Example: the alkali sodium hydroxide is corrosive even at 0.5 mol Dm-3 but the acid hydrochloric needs to be > 6.5mol Dm-3 before being classified as corrosive
     • NaOH + aq -> Na (aq)+ OH- (aq)

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