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The Periodic Table Chemistry-Data-Booklet-20 (Trends (Across Period 3),…
The Periodic Table 
Elements are arranged in increasing order of proton number. Vertical columns are called groups and horizontal rows are called periods. Elements are further grouped into four blocks (s,p,d,f)
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Trends (Down a Group)
Atomic radius increases down the group as increase in number of inner shells, valence electrons are further away from the nucleus and shielding effect outweighs the effect of increase in nuclear charge
1st ionisation energy decreases down the group as similarly increase in shielding effect results in less energy required to remove the valence electron
Electronegativity decreases down the group as similarly increase in shielding effect now decreases the ability of an atom to attract bonding electrons to itself.
Melting point, Electrical Conductivity,
Na, Mg, Al has high melting points due to their structures. There is an increase in electrical conductivity from Na to Al.
Si has the highest melting point due to its giant molecular structure. Si is a semi-conductor/metalloid
P4,S8 and Cl2 have non-polar molecular structures with weak instantaneous dipole-induced dipole attractions between molecules. Hence low melting points. As simple molecules, they have no delocalised electrons to conduct electricity at all.
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Ionic radius: 1. Cationic radius is smaller than corresponding parent atom and Anionic radius is greater than corresponding parent atom. 2. Ionic radius of isoelectronic ions decrease across the period
Trends (Across Period 3)
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Na2O reacts vigorously and exothermically whil MgO has a slow reaction. Al2O3 and SiO2 do not react with water. P4O10 reacts vigorously while SO3 reacts vigorously and exothermically. Na2O dissociates completely in water with a vigorous reaction while MgO is only slightly soluble in water.
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NaCl dissociates completely in water. MgCl2 undergoes partial hydrolysis due to Mg2+ having a higher charge density than Na+. AlCl3 undergoes a larger extent of hydrolysis with water, but when only adding a few drops of water, there will be a violent reaction. SiCl4 undergoes complete hydrolysis. PCl5 also undergoes complete hydrolysis to form a strongly acidic solution. (Take note when only a limited amount of water is added!)