Introduction Now a days scientist had found 116 elements whichhave their own symbol and 92 elements are naturaland 24 elements are artificial. About 150 years agoscientist were trying to group elements together butthey failed. In 1869 one scientist name Mendeleyevhad found a best method to group those elements baseon their atomic number and known as “Periodic Table”.
Periodic Table Periodic table is a tabular display of the chemicalelements, organized on the basis of their atomicnumbers, electron configurations, and recurringchemical properties. In 1860 more than 100 Europeanscientist met for the first time to decide how to grouphow to organise the elements including AlexanderChancourtois, Dmitri Mendeleyev, Henry Moseley,Johann Dobereiner, John Newlands and Lothan Meyer.
Sir William Crooks atomic modelDmitri MedeleyevJohn D. ClarckDifferent designs prepared forthe periodic table
Grouping Elements Periodic table are divided into 18 groups and 7periods. Energy level of elements increase from top tobottom of the periodic table and atomic number of theelements increase from left to right, top to bottom ofthe periodic table. Many elements in the periodic tableare metals. Other are non metal and metalloid.Metalloid is an element with properties intermediatebetween those of a metal and non metal. For example:silicon, boron and germonium.
Group A group is a vertical column in the periodic table.Elements which is in same group have similarcharacteristic. They also have same number ofelectron. From top to bottom in a group, the atomicradii of the elements increase.
Period A period is a horizontal row in the periodic table.There are 7 periods in periodic table. Elements in thesame period show trends in atomic radius, ionizationenergy, electron affinity, and electronegativity. Movingleft to right across a period, atomic radius usuallydecreases.
Metal 70 % of the elements in periodic table are metal. Theyoccupy the left-hand side of the periodic table. Characteristic of metal:• They are shiny• They conduct electricity and heat well• They are found as solid at room temperature• They lose electrons easily• They can hammered into shape• They can be pulled into the shape of wires• They don’t form compounds with each other.
Non metal Characteristic of non metal:• Rarely have metallic luster (shine)• Generally gases at room temperature• Neither malleable nor ductile• Brittle and dull• Poor conductors of heat and electricity• Usually exist as molecules in their elemental form• Combine with other nonmetals to form covalent• Generally form negative ions, e.g. Cl-, SO42-, and N3-• High electronegativity• High ionization energy• Small atom size• Gain electrons to complete their octet• Low boiling and heating points• Mostly in liquid or gas form