PERIODIC TABLE

Introduction:

• In nineteenth century, chemists devoted much of their efforts in attempts to arrange elements in a systematic manner.                                                                                       
• These efforts resulted in discovery of periodic law.
• On the basis of this law, the elements known at that time, were arranged in the form of a table which is known as periodic table.

1)Periods: 

• The horizontal rows of the table are called periods.
• Each period corresponds to the number of electron shells in an atom.    Example:-   
• Elements in Period 1 have one elecron shell, while elements in Period 7 have seven.                       
• 2)Groups:
• The vertical columns are known as groups. 
• Elements within the same group share similar chemical properties.  
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• Example:
• Group 1 elements (alkali metals) are highly reactive, while Group 18 elements (noble gases) are inert and non-reactive. 

• 3)Blocks:
• The table is divided into blocks based on electron configuration: s-block, p-block, d-block, and f-block.
•  These blocks help in understanding the filling order of electrons in atomic orbitals. 
  

Key Sections of the Table

• Alkali Metals (Group 1):
• These are soft, highly reactive metals. 
• Examples:             
•  lithium (Li), sodium (Na), and potassium (K). 
• They react vigorously with water and are used in various applications, from batteries to fertilizers.
• Transition Metals (d-Block):
• These metals, such as iron (Fe), copper (Cu), and gold (Au), are known for their ability to form various oxidation states and complex ions. 
• They are crucial in industrial processes and technology.

• Halogens (Group 17):
• Halogens, including fluorine (F), chlorine (Cl), and bromine (Br), are highly reactive nonmetals.
•  They are used in disinfectants, pharmaceuticals, and chemical synthesis.
• Noble Gases (Group 18):
• Noble gases like helium (He), neon (Ne), and argon (Ar) are inert and don’t typically form compounds.
•  They are used in lighting, cryogenics, and as protective gases in various processes.                                   
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Salient Features of Long Form of Periodic Table:

 This table consists of seven horizontal rows called periods.

 First period consists of only two elements. Second and third periods consist of
8 elements each. Fourth and fifth periods consist of 18 elements each. Sixth period has 32 elements while seventh period has 23 elements and is incomplete.

Elements of a period show different properties.

 There are 18 vertical columns in the periodic table numbered 1 to 18 from left to     right, which are called groups.

 The elements of a group show similar chemical properties.

 Elements are classified into four blocks depending upon the type of the subshell which gets the last electron.