Periodic table

• elements are arranged in order of their proton number in the periodic table.
• A proton is a positively-charged particle found in the nucleus of an atom
• electrons are negatively-charged particles that orbits the nucleus of an atom
• atomic mass - atomic number = neutrons
• the elements on the left side of the periodic table have low melting points, low boiling points and are non-metals
• the elements on the right side of the periodic table have high melting points, high boiling points and are metals
• Trends across the period, several changes are observed such as :

  1)The proton number increases

  2)The number of valence electrons increases

  3)The element changes from metals to non-metals

  4)The element changes from being a good conductor of electricity(metals) to being a poor conductor of electricity(non-metals)
• Trends down the group, elements in the same group exhibit similar properties :

  1)All elements in the same group have the same number of valence electrons

  2)The elements usually form ions with the same charge. eg, all elements in group 1 form ions with a charge of +1

  3)All elements in the same group have the same chemical properties

  4)All elements in the same group have similar physical properties

  5)The elements form compounds with a similar chemical formula
• Group 1(1)

  1)group 1 elements are also known as alkali metals

  2)all elements in the group form ions with a charge of +1, eg, potassium ion exists as K+

  3)alkali metals are soft shiny solids

  4)alkali metals conduct electricity
• Group 1 (2)

  5)grp 1 metals have low densities and low melting points

  6)they react with cold water very vigorously to form an alkaline solution of the metal hydroxide and hydrogen gas

  7)the reactivity of grp 1 metals increase down the group

  8)grp 1 metals special trend is that its melting points of the elements decreases down the group
• Group VII (group 7) : Halogens


  The groups number always indicates the number of electrons present in the outermost shell, hence, halogens have 7 electrons in their outermost shell, this means that they will need to accept one more electron to achieve a stable configuration.
• Group VII (group 7) : Halogens

  1)The halogens are non-metals with low melting and boiling points.

  2)Halogens exists as diatomic molecules. eg, F2, Cl2, Br2, I2.
• Group VII (group 7) : Halogens

  Fluorine - F2 -- pale yellow --- physical state at room temp : gas

  Chlorine - Cl2 -- yellowish-green --- physical state at room temp : gas

  Bromine - Br2 -- reddish-brown --- physical state at room temp : liquid

  Iodine - I2 -- purplish-black --- physical state at room temp : solid

  Astatine -At2 -- black --- physical state at room temp : solid
• Halogens trends observed down the group :

  1)melting and boiling points increase down the group

  2)the colour of the elements become darker down the group

  3)the elements become less reactive down the group
• Displacement reaction of halogens

  halogens undergo displacement reactions, this is a process whereas a more reactive element will displace a less reactive element from a solution of its salt.

  For exp, since chlorine is more reactive than bromine, chlorine will 'kick out' bromine and replace it. Furthermore, since there is bromine released, the solution now turns reddish-brown because it is no longer an ion.
• Group VIII (group 8) : Noble gasses/ Inert gasses/ Rare gasses

  1)they are unreactive as the elements in the group have full outermost shell of electrons. Hence, they do not need to react with any other elements in order to become stable.

  2)they are monoatomic gasses, which means they stand alone. For exp, argon is Ar while Krypton exists as Kr

  3)colourless gasses at room temperature

  4)insoluble in water
• Group VIII (group 8) : Noble gasses -- uses


  Helium --> balloons

  Neon --> neon lights and signs

  Argon --> used to fill light bulbs to protect the filament

  Krypton --> Space fuel for rockets, also used as lasers
• acids


  sulfuric acid --> sulfate

  nitric acid --> nitrate

  hydrochloride acid --> chloride
• alkali


  oxides

  hydroxide

  ammonia gas