Periodic table
● The columns are groups and the rows are periods
● Mass no.
○ Nucleon no. → number of protons and neutrons
○ The no. of protons and neutrons present in the nucleus of an atom
● Atomic no.
○ No. of protons
○ The no. of protons present in the nucleus of an atom
● Valency of an element is the number of electrons its atoms lose or gain to form a compound
● Upto = 2n^2
● Columns → groups → no. of electrons in outer shell
● Rows → periods → gives you the no. of shells present in the atom
Group 1 (Alkali metals)
● Group 1 metals have 1 electron in outermost shell
● The relative molecular mass increases down the group
● Trends
○ Mp/Bp decreases down the group
○ Density increases down the group
○ Reactivity increases down the group
○ Becomes softer down the group
● The alkali metals react vigorously with water giving out hydrogen bubbles, leaving solutions of
their hydroxides which are alkalis
● Alkali metals when reacted with chlorine burst into flames, they burn brightly, forming chlorides
● Alkali metals burst into flames when you heat them and put it in a jar of oxygen, they burn
fiercely to form oxides
● Atoms with the same number of valence electrons react in a similar way
● The alkali metals are the most reactive of all metals as they need to lose only one electron to gain
a stable outer shell
● The alkali metals form ionic compounds, in which the metal ion has a charge of 1+. The compounds
are white solids. They dissolve in water to give colourless solutions
Group 2 (Alkaline Earth metal)
● They react with oxygen to form metallic oxides and react with water to form hydrocarbons
● Valency = +2
● Outer Shell = 2
● Trends
○ Melting point decreases down the group
○ Density increases down the group
○ Reactivity increases down the group
● Uses
○ Calcium used in body for bones and teeth
○ Beryllium is used to make jewelry and emeralds
○ Magnesium is used to make medicines
Group 7 (Halogens)
● Outer shell = 7
● Valency = -1
● Trends
○ Colour gets deeper down the group
○ Density increases down the group
○ Boiling point increases down the group
○ Reactivity decreases down the group
● Halogens react with metals to form compounds called halides
● A halogen will displace a less reactive halogen from a solution of its halide
Group 8 (Noble gases)
● Group 8 either has 2 or 8 electrons in their outermost shell that allows them to be stable
● Properties
○ Non-metals
○ Colourless gases
○ Monatomic gases
○ Unreactive because their atoms already have stable outer shells
● Trends
○ The atoms increase in size and mass down the group
○ Density of gases increases down the group
○ B.P increases down the group
● Uses
○ Helium → balloon, airships
○ Argon → tungsten bulbs
○ Neon → Glows red
○ Krypton → lasers
Transition metals
● Properties
○ Hard, tough and strong
○ High m.p
○ Malleable and ductile
○ Good conductors of electricity and heat
○ High density
● Chemical properties
○ They are much less reactive than Group 1 metals
○ They show no clear trend in reactivity
○ Most transition elements form coloured compounds
○ Most can form ions with different charges
○ They can form more than one compound with another element
○ Transmission elements have variable oxidation states
○ Most transmission elements can form complex ions
● Uses
○ Used in structure like bridges and buildings in form of steel (alloy)
○ Help in making alloys
○ Used as conductors of heat and electricity
○ Many transition elements and their compounds act as catalysts
