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# Periodic Table Metals

Metals form around 24% mass of earth with most abundant in aluminium, iron, calcium, magnesium and sodium. Our periodic table, they are comprised of approximately two third of all the known elements. They occur in nature sometimes free but mostly in combined state. The earth crust is the biggest source of metals. They are found everywhere around us from machines to tools and from jewellery to automobiles.

Metals have wide range of properties such as hardness, brittleness, tensile strength, electrical and thermal conductivity etc. which make use of them in almost every field.

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## Metals Definition

A metal is solid hard shiny element possessing characteristic properties such as thermal and electrical conductivity, malleability, and ductility. In periodic table, metals are alkali metals, alkaline earth metals, transition metals and rare earth metals.

Metals are electropositive elements i.e. they form positive ions (cations). Therefore metals can also be defined as substance which is hard and lusturous, malleable and ductile with high electrical and thermal conductivity which loses electrons to form cations.

## Types of Metal

There are broadly three types of metal. In the periodic table they are:

Alkali metals:

Alkali metals constitutes the first group of periodic table containing elements lithium( Li), potassium (K), sodium (Na), caesium(Cs), rubidium (Rb) and francium (Fr). These metals are also called s- block elements as the last electron in them enters the s-orbital with general electronic configuration [noble gas] $ns^{1}$.

They have the largest size in the periodic table and are highly reactive. Because of high reactivity, these metals form alkaline oxides and hydroxide. That is why they are called alkali metals. The alkali metals are soft with relatively low melting and boiling point.

Alkaline earth metals:

The alkaline earth metals belong to the second group of periodic table with six metallic elements. These are beryllium (Be), barium (Ba), calcium (Ca), magnesium (Mg), strontium (Sr) and radium (Ra)

They are also called the s - block elements as their last electron enters in s-subshell with general electronic configuration [noble gas] $ns^{2}$. These metals are called alkaline earth metals because they existed in the earth and were alkaline.

They are harder and are less reactive than alkali metals. Their melting point and boiling point are also higher than alkali metals.

Transition metals:

The transition metals are those metals which have partly filled d sub shell. There is exception to the above definition, as zinc, cadmium, mercury do not have incomplete d subshell, yet they are called transition metals.

These metals are quite shiny and have high melting and boiling point. Except for mercury all transition elements have metallic structure. They are electropositive and show some characteristic properties such as catalytic property, forming coloured ions, magnetic properties, variable oxidation states etc.

Other metals or post transition metals:

These are the metals which are located between the transition metals and the metalloids. All these metals are solid, opaque and have high density.

## Metal in Chemistry

Metals in chemistry have broad place. Metals have low ionization energies, low affinity, low electronegativity which are responsible for their high electrical and thermal conductivities, metallic lustre and hardness, malleability and ductility. It is due these properties of metals which make them quite useful.

Some metals due to their catalytic properties are useful for many reactions. For example, platinum is a catalyst used particularly in Contact process involving combination of sulphur dioxide and oxygen to yield sulphur trioxide.

A metal in combination with different metals forms alloys. These alloys have diverse uses. Certain alloys are even harder or stronger than their corresponding metals.

For example, Duralumin, alloy of Aluminium, Copper, Magnesium and manganese is used for making aeroplanes, automobile parts etc.

Similarly, different alloy steel is obtained by adding different metals in varied composition. Alloy steel find many uses from cutlery, making cables, tools, watches, cutting machines etc.

## Transition Metal Chemistry

The transition metals are defined as metals with partly filled (n-1) d sub shell. If the d sub shell is completely filled, the elements are known as d – block or transition elements. Below are some of the characteristics of transition metals.
• All the transition metals have metallic structure except for mercury which is liquid.
• They are malleable and ductile and form alloys with several other metals.
• They are good conductor of heat and electricity. Copper, gold and silver are particularly good in their thermal and electrical conductivity.
• Most of the transition metals and their compounds have catalytic properties.
• For example, Iron is used in the synthesis of ammonia by Haber’s process, molybdenum is used as a promoter, Nickel in the hydrogenation reactions, Vanadium pentaoxide (V2O5) in the manufacture of ammonia.
• Most of the transition metal compounds are coloured. This is because of the incomplete d orbitals.
• Another property of transition metals is tendency to form coordination complexes. For example $[Fe (CN)_{6}]^{3}$ - , $[PtCl4]^{2}$-. The tendency to form complexes is due to two factors. Firstly due to small size of the ions and secondly they have vacant orbitals.
• Due to presence of unpaired electrons in the (n-1) d orbitals, most of the transition metal ions and their compounds are paramagnetic.
• The transition metals show a large number of oxidation state which are related to electronic configurations. The stability of any oxidation state depends on its electrode potential.

## Physical Properties of Metals

All the metals have some similar physical properties. The basic physical properties are:
1. Density - Metals have high density.
2. Hardness - All metals are hard except alkali metals which are soft and can be cut through knife.
3. Ductile - All metals posses the property called ductility i.e. they can be drawn into wires.
4. Malleability - Metals are malleable as they can be hammered into sheets.
5. Conductivity - Metals are good conductor of heat and electricity. Copper and aluminium wires are used in electrical appliances and electrical cables.
6. Boiling and melting point - The metals have higher boiling and melting points. However alkali and alkaline earth metals have relatively low boiling and melting points.
7. Shine - Metals are shiny and lustrous. It is this property which makes use of them in jewellery. Gold and silver are particularly used for jewellery and decorations.
8. Tensile strength - Some metals like copper, platinum and iron have greater tensile strength i.e. they can be stretched to several degrees.

## Chemical Properties of Metals

Metals are electropositive in nature. They have a tendency to lose electrons as their electronegativity is low. The chemical properties of metals are given below.

• Reaction with water:
Metals react readily with water forming metal oxides or metal hydroxides and evolving hydrogen. For example,

$2Li + 2H_{2}O \rightarrow 2LiOH + H_{2}$

$3Fe + 4H_{2}O \rightarrow Fe_{2}O_{3} + H_{2}$

• Action of air:
Metals have a tendency to get tarnished in air.  They react with oxygen forming oxides.

$2 Cu + O_{2} \rightarrow 2CuO$

$4Al + 3O_{2} \rightarrow 2Al_{2} O_{3}$

The reactivity of different metals with oxygen is different. Some metals specifically the alkali metals react vigorously with oxygen and catch fire.

Metals such as lead, zinc, aluminium etc have an ability to form protective layer of oxide over them which prevents them from further reaction.

• Action with hydrogen:
Some metals react with hydrogen to form hydrides which are ionic in nature. For example,

$Ca + H_{2} \rightarrow CaH_{2}$
• Reaction with dilute acids:
Metals react with dilute acids to form metal chlorides and hydrogen.

$2Na + 2HCl \rightarrow 2NaCl + H_{2}$

$Mg + 2HCl \rightarrow MgCl_{2} + H_{2}$
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