Metallic & nonmetallic property , Acidic & basic property in the periodic table

At the beginning of the nineteenth century Berzelius was the first scientist who classified elements into two main group ( metals and nonmetals ) , according to their physical properties , Indeed that was before knowing anything about atomic structure , This is an old classification which is still currently in use , although there are no boundaries between them and their properties in the periodic table .

With the development of our concept about the electron structure of atoms , we can differentiate between metals and nonmetals , Additionally , there is a third group of elements known as metalloids .

Metals

Their valence shell – generally – has less than half its capacity of electrons , They have large atomic radius which leads to small values for ionization energy and electron affinity .

They are electropositive elements , due to their tendency to lose electrons of the valence shell and change into positive ions to reach the structure of the nearest noble gas .

They are good electric conductors , due to the mobility of their few valence electrons , which can transfer from one position to another in the metal structure .

Metallic and nonmetallic property

Metallic and nonmetallic property

Nonmetals

Their valence shell – generally – has more than half its capacity of electrons , They have small atomic radius which leads to high values for ionization energy and electron affinity .

They have small atomic radius which leads to high values for ionization energy and electron affinity , They are electronegative elements , due to their tendency to gain electrons to form negative ions that have the same electron structure of the nearest noble gas .

They do not conduct electricity ( electric insulators ) , because their valence electrons are strongly bound to the nucleus , Thus , it is difficult for these valence electrons to be transferred .

Metalloids

The metalloids are characterized by the following properties :

They have the metallic appearance and the most properties of nonmetals , Their electronegativity is intermediate between metals and nonmetals , Their electric conductivity is less than that of metals , but more than that of nonmetals , They are used in manufacturing electronic instruments parts – such as transistors – as they are semiconductors .

Metalloids are a group of elements that has a metallic appearance and most of the properties of nonmetals which characterized by their electronegativity is intermediate between metals and nonmetals and their electric conductivity is less than that of metals , but more than that of nonmetals .

The graduation of metallic and nonmetallic property in the periodic table :

In the same group : The metallic character increases ( The nonmetallic character decreases ) with the increase in the atomic number as we go down the group , due to their large atomic radius and the low ionization potential and electron affinity .

In the same period : The period begins by the strongest metals in group 1A , then the metallic property decreases gradually by increasing the atomic number across the period till we reach the metalloids , To the right of the metalloids begins the nonmetallic property , The period ends by the elements of the highest nonmetallic property in group 7A .

Consequently : Cesium is considered the most active metal , because the metallic property increases at the same group by increasing the atomic number and it is placed at the bottom of the left hand side the table ( the lowest metal in ionization potential ) .

Fluorine is considered the most active nonmetal , because the nonmetallic property decreases at the same group by increasing the atomic number and it is placed at the top of the right side of the table ( the most electronegative nonmetal ) .

The graduation of metallic and nonmetallic property in the third period , It is clear that by increasing the atomic number , the metallic character decreases and the nonmetallic character increases .

Acidic and basic property

When an element combines with oxygen forming a compound known as oxide , There are types of element oxides which are Acidic oxides , Basic oxides and Amphoteric oxides .

Acidic oxides

The nonmetallic oxides are named by acidic oxides , because :

They dissolve in water forming oxygenated acids .

CO2 ( g ) + H2O ( l )  H2CO3 ( aq )

SO3 ( g ) + H2O ( l )  H2SO4 ( aq )

They react with alkalis forming salt and water .

CO2 ( g ) + 2NaOH ( aq ) Na2CO3 ( aq ) + H2O ( l )

From the acidic oxides , Carbon dioxide CO2 , Sulphur trioxide SO3 , Nitrogen dioxide NO2 .

Basic oxides

The metallic oxides are usually known as basic oxides , Some basic oxides are not soluble in water and others are soluble in water forming alkalis , the water soluble basic oxides are also known as alkali oxides .

K2O ( s ) + H2O ( l ) 2KOH ( aq )

H2O ( l ) + Na2O ( s ) 2NaOH ( aq )

From the basic oxides , Potassium oxide K2O , Sodium oxide Na2O , Magnesium oxide MgO .

They react with acids forming salt and water :

2HCl ( aq ) + Na2O ( s ) 2NaCl ( aq ) + H2O ( l )

MgO ( s ) + H2SO4 ( aq ) MgSO4 ( aq ) + H2O ( l )

Amphoteric oxides

Amphoteric oxides are element oxides that react with acids as basic oxides and react with bases as acidic oxides forming in both cases salt and water .

ZnO ( s ) + H2SO4 ( aq ) ZnSO4 ( aq ) + H2O ( l )

ZnO ( s ) + 2NaOH ( aq ) Na2ZnO2 ( aq ) + H2O ( l )

Amphoteric oxides such as Aluminum oxide Al2O3 , Zinc oxide ZnO , Antimony oxide Sb2O3 , Tin oxide SnO .

The graduation of acidic and basic property in the periodic table :

In the period : The basic property of the oxide decreases as the atomic number of the element increases , while the acidic property increases .

In the group : where in the group which starts by a metal , the basic property of the oxide increases as the atomic number increases as in group 1A .

In the group which starts by a nonmetal , The acidic property of the oxide increases as the atomic number increases as in group 7A .

The graduation of acidic and basic property in the third period , As the atomic number increases the basic property decreases and the acidic property increases .

The acidic property of hydrogen compounds of group 17 ( halogens ) increases as the atomic number increases , Because the increase in the atomic number in the group leads to the increase in the atomic size of halogen and then its attraction force for hydrogen atom decreases , making it easier to be ionized .

Radius property , Ionization potential , Electron affinity & Electronegativity

Modern periodic table and classification of Elements

Hydroxy compounds , Rules for calculating the oxidation numbers

You may also like...

Leave a Reply

Your email address will not be published. Required fields are marked *