ATOM & STOICHIOMETRY

ATOM & STOICHIOMETRY

1. MATTER

   • Occupies space & mass exist everywhere exc. vaccum solid, liquid & gas
   • pure subtances
     • element
       •  is a substance that cannot be separated into simpler substances by chemical means 
     • compound
       • a substance composed of atoms of two or more elements chemically united in fixed proportions
   • mixtures
     • homogenous
     • heterogenous
       • wet sand

2. ATOM

   •  The smallest unit of an element. Consists of a nucleus and electrons.   Atom cannot be created, destroyed or split.
   • molecules
     •  Two or more atoms combine together(held together by a strong chemical bond) i.e. H2, O2, N2
   • ions
     • charged atom
     • cation (+)
       •  an atom that has lost one or more electrons making it positively charged.
     • anion (-)
       • an atom that gained one or more electrons making it negatively charged 
     • polyatomic ion
       •  ions that contain two or more atoms in it.  e.g: OH- , NO3-, CO32-, NH4+ 

3. FUNDAMENTAL PARTICLES

   •  Also known as subatomic particles   A typical atom consists of a nucleus composed of positively charged protons and neutral neutrons surrounded by a cloud of orbiting negatively charged electrons   Proton and neutrons join together to form a nucleus and are called as nucleons 
   • electron
     • Symbol e-   Mass (kg) 9.109 × 10-31   Approximate relative mass (a.m.u.) 0.0  Electric Charge -1 
   • neutron
     • Symbol  [n]   Mass (kg)  [1.675 × 10-27 ] Approximate relative mass (a.m.u.)   [1.0]   Electric Charge  [0] 
   • proton
     • Symbol  p+    Mass (kg)  1.673 × 10-27   Approximate relative mass (a.m.u.)   1.0 Electric Charge +1
   • electric & magnetic field
     •  The beam of electrons and protons are deflected when fired through electric or the magnetic field whereas the neutron are not deflected   This showed that both electrons and protons have charges   Electrons are lighter than proton because it deflected much more in the electric and magnetic field 

4. PROTON NUMBER

   •  Is the number of protons found in the nucleus of an atom   identical to the charge number of the nucleus    Atom is neutral particles. Hence, the number of protons in the molecules of an atom is the same as the number of electrons surrounding the nucleus   Example: atomic number of nitrogen (N) is 7. So nitrogen contains 7 protons and 7 electrons  The atomic number uniquely identifies a chemical element   So each element has different proton number that are arranged in an ascending order 
   • atomic number

5. NUCLEON NUMBER

   •  Total number of protons and neutrons present in the nucleus of an atom of an element   Nucleon number = Number of neutrons + Proton number = number of neutrons + atomic number 
   • USES:  gives a useful rough figure for the atomic mass  Are used to identify isotopes  
   • mass number
   • A-Z

6. ISOTOPES

   •  Are atoms of the same element that contain the same number of protons but different number of neutrons   Have same chemical properties( because they are atoms of the same element) but different physical properties  Different isotopes of the same element cannot have the same nucleon number, but isotopes of different elements often do have the same mass number
   • stable
     •  Stable isotope will not disintegrate the nuclei spontaneously
   • unstable
     •  Unstable isotopes known as radioactive isotopes will disintegrate spontaneously to form a new nucleus (new element)   If the new nucleus that formed are also not stable, it will further decay until a new stable nucleus is obtained.   The disintegration of the isotope will emits electromagnetic waves  
     • alpha
     • beta
     • gamma