The document summarizes trends in properties across the periodic table, including atomic radius, ionization energy, electronegativity, and melting/boiling points. It also describes common reactions of elements such as sodium, magnesium, aluminum, silicon, phosphorus, and sulfur with water, oxygen, and chlorine. These properties and reactions follow predictable trends based on an element's position in the periodic table.

1. Periodic Table
Definition:
 Tabular arrangement of elements on the basis of ascending Atomic No.

2. Demarcation of Periodic Table

3. Atomic radius
• Explaining the increase in atomic radius
Down the group: atomic radius increases
Due to:
(i) no of shell increases
(ii) nucleus hold decreases
(iii) electronic cloud increases

4. Compare lithium and sodium:
• Li
• 1s22s1
• Na
• 1s22s22p63s1

5. Atomic radius
• Across the period
• Atomic radius decreases
Due to:
(i) no of shell remains constant
(ii) nuclear charge increases (electrons are pulled closer to the nucleus)

6. Ionization Energy
• the minimum amount of energy needed to
remove an electron from the outermost shell
of its isolated gaseous atoms in its ground
state
• Na Na1+ + 1e- I= 496kj/mol
Mg Mg+ + 1e- I1= 738kj/mol
Mg Mg2+ + 2e- I2= 1451kj/mol

7. Explaining the decrease in first
ionisation energy
• Down the Group
• Ionisation energy is governed by
• the charge on the nucleus,
• the amount of screening by the inner electrons,
• the distance between the outer electrons and the
nucleus.
• However, as you go down the Group, the distance
between the nucleus and the outer electrons
increases and so they become easier to remove -
the ionisation energy falls.

8. Explaining the decrease in first
ionisation energy
• Across the Period
• No of shell remains constant
• Nuclear charge increases(nucleus hold become stronger)
• Shielding effect is not very effective
• Hence
ionization energy increases

9. Trends in Electronegativity
.
• Electronegativity is a measure of the tendency
of an atom to attract a bonding pair of
electrons.
• Most electronegative element in the periodic
table is Fluroine

10. Trends in Melting and Boiling Points
• Variation in the Group
Due to increase in atomic size binding forces(mettalic
bond) become weaker in large size atoms
The atoms in a metal are held together by the attraction
of the nuclei to the delocalised electrons. As the
atoms get bigger, the nuclei get further away from
these delocalised electrons, and so the attractions fall.
That means that the atoms are more easily pulled
apart

11. Trends in Melting and Boiling Points
• IN GROUP VIIA
• MP AND B.P INCREASES DOWN THE GROUP
• LARGE MOLECULES EXERT GREATER FORCE OF
ATTRACTION DUE TO THEIR HIGHER
POLARIZABILITIES

12. Trends in Melting and Boiling Points
• VARIATION IN THE PERIOD
• MP AND BP INCREASE UPTO- IVA( VALENCE ELCTRON
INCREASES)
• MP OF IIA>IA
• CARBON HAS MAX. VALENCE ELECTRON
• DIAMOND HAS GIANT STRUCTURE SO HIGH MP
• MP AND BP DECREASES ONWARD UPTO-VIIIA
• SMALL COVALENT MOLECULE,WEAK INTER
MOLECULAR FORCES

13. Reaction with water
• Reactions with water
• Sodium
• Sodium has a very exothermic reaction with cold water producing hydrogen and
a colourless solution of sodium hydroxide.
• Magnesium has a very slight reaction with cold water, but burns in steam.
• A very clean coil of magnesium dropped into cold water eventually gets covered in small
bubbles of hydrogen which float it to the surface. Magnesium hydroxide is formed as a
very thin layer on the magnesium and this tends to stop the reaction.
• Magnesium burns in steam with its typical white flame to produce white magnesium
oxide and hydrogen.

14. Reaction with water
• Aluminium
Aluminium powder heated in steam produces hydrogen and aluminium oxide. The
reaction is relatively slow because of the existing strong aluminium oxide layer on
the metal, and the build-up of even more oxide during the reaction.
silicon will react with steam at red heat to produce silicon dioxide and
hydrogen.
• Si +H2O SiO2 + H2
Phosphorus and sulphur
• These have no reaction with water

15. Reaction with water
Chlorine dissolves in water to some extent to give a green solution. A reversible
reaction takes place to produce a mixture of hydrochloric acid and chloric(I) acid
(hypochlorous acid).
• In the presence of sunlight, the chloric(I) acid slowly decomposes to produce more
hydrochloric acid, releasing oxygen gas, and you may come across an equation
showing the overall change:
• Argon
• There is no reaction between argon and water.

16. Reaction with oxygen
• Reactions with oxygen
• Sodium
• Sodium burns in oxygen with an orange flame to
produce a white solid mixture of sodium oxide
and sodium peroxide.
• For the simple oxide:
• For the peroxide:
• MagnesiumMagnesium burns in oxygen with an
intense white flame to give white solid
magnesium oxide.

17. Reaction with oxygen
Aluminium will burn in oxygen if it is powdered, otherwise the strong
oxide layer on the aluminium tends to inhibit the reaction.
•
Silicon will burn in oxygen if heated strongly enough. Silicon dioxide is
produced.
White phosphorus catches fire spontaneously in air, burning with a
white flame and producing clouds of white smoke - a mixture of
phosphorus(III) oxide and phosphorus(V) oxide.

18. Reaction with oxygen
• Sulphur
Sulphur burns in air or oxygen on gentle heating with a pale blue
flame. It produces colourless sulphur dioxide gas.
.Chlorine and argon
chlorine won't react directly with oxygen. Argon doesn't react either.

19. Reaction with chlorine
• Reactions with chlorine
• Sodium
• Sodium burns in chlorine with a bright orange flame. White solid sodium chloride is produced.
•
• Magnesium
• Magnesium burns with its usual intense white flame to give white magnesium chloride.
•
• Aluminium
• Aluminium is often reacted with chlorine by passing dry chlorine over aluminium foil heated in a
long tube. The aluminium burns in the stream of chlorine to produce very pale yellow aluminium
chloride. This sublimes (turns straight from solid to vapour and back again) and collects further
down the tube where it is cooler.
• Note: You may find versions of this equation showing the aluminium chloride as Al2Cl6. In fact, this
exists in the vapour at temperatures not too far above the sublimation temperature - not in the
solid. The structure of aluminium chloride is discussed on the page about Period 3 chlorides.
• If you follow this link, use the BACK button on your browser to return to this page.

20. Reaction with chlorine
• Silicon
• If chlorine is passed over silicon powder heated in a tube, it reacts to produce silicon tetrachloride. This is a
colourless liquid which vaporises and can be condensed further along the apparatus.
•
• Phosphorus
• White phosphorus burns spontaneously in chlorine to produce a mixture of two chlorides, phosphorus(III)
chloride and phosphorus(V) chloride (phosphorus trichloride and phosphorus pentachloride).
• Phosphorus(III) chloride is a colourless fuming liquid.
• Phosphorus(V) chloride is an off-white (going towards yellow) solid.
• Note: These equations are often given starting from P rather than P4. It depends which form of phosphorus
you are talking about.
• If you are talking about white phosphorus (as I am here), P4 is the correct version. If you are talking about
red phosphorus, then P is correct. Red phosphorus has a different (polymeric) structure, and P4 would be
wrong for it.
• In my experience, red phosphorus is less commonly used in labs at this level (it isn't as excitingly reactive as
white phosphorus!)

21. Reaction with chlorine
Chlorine
If a stream of chlorine is passed over some heated sulphur, it reacts to form
an orange, evil-smelling liquid, disulphur dichloride, S2Cl2.
• Chlorine and argon
• It obviously doesn't make sense to talk about
chlorine reacting with itself, and argon doesn't
react with chlorine.