Periodic table explained

1. Periodic Table

2. Periodic Table
• The Progenitor Periodic Table
• First periodic table made by Dimitri Mendeleev in 1869.
• The Modern Periodic Table
• Differences to Mendeleev’s:
– 115 elements while for Mendeleev’s is 69.
– Mendeleev arranged the elements according to relative atomic
mass while today we arrange according proton number.
• Period – horizontal row of elements in periodic table.
• Group – vertical column of elements in periodic table numbered
from 0 to 10 Elements between Group II and Group III – Transition
metal.

3. Patterns in the Periodic Table
1. Electronic Structure
• Elements in same group has the same
number of valence shell electrons
which the amount is the same as the
group number.
• e.g. Group II has elements with valency
of 2 electron.

4. 2. Charges On Ions
• The charges relates to the group number
and number of valence electrons.
• Elements on left side periodic table lose
ions to form cation.
• Elements on right side periodic table lose
ions to form anion.
• electrons depending on reacting element.
• Transition metals may form variable cation
of 2+ or 3+.

5. 3. Bonding
• Elements in same group form same type and number of
bonds due to the same number of valence electrons.
• e.g. Sodium in Group I forms NaCl, so other elements in
Group I does the same.
• (RbCl, KCl, LiCl, CsCl)

6. 4. Metals and Non-metals
Metals Non-metals
On the left side of periodic table On the right side of periodic table
Have fewer ( 4) valence electrons Have more (>4) valence electrons

7. 5. Changes in Group
• Proton number increases going down the group
• On each side of periodic table the change of the
proton number small & gradual
• In transition metal the gradual change is larger.

8. Predicting Properties
1. Farmula and structure
• Given chlorine iodine bromine of Group VII forms
molecules of Cl2, I2 and Br2 respectively predict the
molecular formula of Fluorine. F2.

9. Properties of elements
• Properties of element changes down the group.
• i.e. given list of group 7 elements, predict the properties
of astatine.

10. Group Properties
1. Group I Elements – The Alkali Metals
• They are very soft metal can easily cut by knife due to weak
metallic bonding.
• One valence electron. Valency is +1 can lose one electron.
• Most reactive metals not found in free state can easily
react with the moisture so they are kept in kerosene oil to
protect them from reacting with air.

11. Group Properties(Alkali Metals)
• They are low density metals even lower than water due to
weak metallic bonding but their densities increases down
the group.
• They are found in combined form.
• Members of this group Li,Na,K,Rb,Cs,Fr,

12. Group Properties(Alkali Metals)
Element Chloride Nitrate Sulphate Oxide
Lithium LiCl LiNO3 Li2SO4 Li2O
Sodium NaCl NaNO3 Na2SO4 Na2O
Potassium KCl KNO3 K2SO4 K2O

13. Group Properties(Alkali Metals)
Name Symbol Density (g/cm3) Melting point
(oC)
Lithium Li 0.53 180
Sodium Na 0.97 98
Potassium K 0.86 64
Rubidium Rb 1.5 39
Caesium Cs 1.9 29

14. Group Properties(Alkali Metals)
Reaction with air
• Explosive reaction.
• Readily catches fire if exposed to air forming white solid
oxide.
• Reactivity increases down the group. The metals at the
bottom will react more expensively than the above one.
• 4Na + O2 → 2Na2O

15. Group Properties(Alkali Metals)
Reaction with cold water
Alkali Metal + water→ Base or alkali + H2
2Na + 2H2O → 2NaOH + H2
Reaction with non metal.
Alkali metal + halogen → salt
2Na + Cl2 → 2NaCl

16. Transition Elements
• Properties
• First transition series are all metals
• Transition elements have high melting points
• They have high density
• They have variable oxidation state, e.g. Iron (Fe) appear as Fe2+ or
Fe3+
• They form coloured compounds, e.g. CuSO4 is blue, FeSO4 is green
• They form complex ions, e.g. MnO -, Manganate(VII) ions They act
as catalysts

17. Uses of Transition Elements
• Most transition elements and their compounds act as
catalysts which speed up chemical reactions.
• Iron is used in Haber Process for manufacture of ammonia
• Vanadium(V) oxide is used in contact process to
manufacture sulphuric acid
• Nickel is used in hydrogenation of alkenes to form saturated
fats (e.g. margarine)

18. Advantages
– Since transition elements speed up chemical processes
in industries, they saves time in manufacture
– Less energy is needed for manufacture in industries,
hence lower cost
– Since less energy is needed, more energy resources
can be conserved, e.g. oil to generate electricity in
producing iron.