What are Representative Elements?
The periodic table is divided into four sections: s, p, d, and f. The elements present in s- and p-blocks except inert gases are collectively known as representative elements or main group elements.
These elements have filled inner orbitals and unfinished outermost orbitals, valence shells. The representative elements or main group elements include all nonmetals and a few metals.
The 18th group elements or noble gases of the periodic table are not part of these representative elements because of their filled valence shells. Also, they do not tend to share or transfer electrons for bond formation.
Table of Contents
- What are Representative Metals?
- Occurrence of Representative Metals
- Preparation of Representative Metals
- Frequently Asked Questions – FAQs
What are Representative Metals
Members of the s block and parts of the p block of the table are representative metals. The list of representative metals is as follows:
- Group 1: Lithium (Li), Sodium (Na), Potassium (K). Rubidium (Rb), Cesium (Cs), Francium (Fr)
- Group 2: Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra)
- Group 13: Aluminum (Al) Gallium (Ga) Indium (In) Thallium (Tl)
- Group 14: Tin (Sn) and Lead (Pb)
- Group 15: Bismuth (Bi)
- Group 12: Zinc (Zn), cadmium (Cd) and mercury (Hg) are considered representative because their last electron enters the s-orbital.
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Occurrence of Representative Metals
Most representative metals do not occur as free elements in nature due to their reactivity. On the other hand, compounds that contain ions of most representative metals are abundant. These metals are found primarily in minerals, with lithium found in silicate or phosphate minerals.
- Sodium and potassium are found in salt deposits from ancient sea evaporation and in silicates.
- Alkaline earth metals exist as silicates, carbonates, and sulphates.
- Beryllium can be found in the mineral beryl, Be3Al2Si6O18.
- Magnesium is found in seawater as silicates, carbonates, sulphates, and heavier alkaline earth metals.
- Aluminium is abundant in many clays as well as bauxite, an impure aluminium oxide hydroxide.
- The oxide cassiterite, SnO2, is the primary tin ore, and the sulphides or products of sulphide weathering are the primary lead and thallium ores.
- The remaining representative metals are found in zinc or aluminium ores as impurities.
Preparation of Representative Metals
Electrolysis
Ions of metals in groups 1 and 2 are extremely difficult to reduce. These elements must be prepared via electrolysis. This method is useful in the extraction of reactive metals such as sodium, aluminium, and magnesium.
Sodium
The electrolysis of molten sodium chloride is the most important method for producing sodium; the setup is a Downs cell.
The electrolysis cell is filled with molten sodium chloride mixed with calcium chloride. When a direct current is applied to the cell, sodium ions migrate to the negatively charged cathode and pick up electrons, converting the ions to sodium metal.
Aluminium
The Hall-Heroult process is widely used in aluminium extraction. Pure Al2O3 is mixed with CaF2 or Na3AlF6 in the Hall-Heroults process. This lowers the melting point of the mixture. A steel vessel with a carbon and graphite rod lining is used.
Magnesium
Magnesium is isolated in large quantities through electrolysis. The main source of magnesium is seawater. Liquid magnesium and chlorine gas are produced when molten magnesium chloride is electrolysed.
MgCl2 + Ca(OH)2 → Mg(OH)2 + CaCl2
Mg(OH)2 + HCl → MgCl2 + 2H2O
MgCl2 → Mg + Cl2
Chemical Reduction
Many of the representative metals can be isolated chemically by using other elements as reducing agents. Chemical reduction is generally less expensive than electrolysis.
Magnesium
The high-temperature reaction of magnesium oxide with elemental silicon produces pure magnesium:
Si + 2MgO → SiO2 + 2Mg
Zinc
Zinc ores are typically zinc sulphide, zinc oxide, or zinc carbonate. After separating these compounds from the ores, heating in air converts them to zinc oxide via one of the following reactions:
2ZnS + 3O2 → 2ZnO + 2SO2
ZnCO3 → ZnO +CO2
Then carbon (in the form of coal) reacts with zinc oxide to produce zinc:
ZnO + C → Zn + CO
Tin
Tin ores containing SnO2 are roasted to remove contaminants such as arsenic and sulphur as volatile oxides. The oxides of other metals are removed from the remaining material by treating it with hydrochloric acid. Then tin is produced by heating purified ore with carbon at temperatures above 1000 °C:
SnO2 + 2C → Sn + 2CO
Frequently Asked Questions on Representative Metals
What is the significance of the term “representative elements”?
The representative elements have completely filled inner orbitals and incomplete outer orbitals or valence shells. Their general properties are expected of the group to which they belong; this is because the representative elements of the same group have similar electronic configurations, with the same number of electrons in their valence shell.
What distinguishes an element as a representative metal?
The representative metals are those whose s and p orbitals are filled. The transition metals are elements that fill the d orbitals (groups 3–11 on the periodic table), and the inner transition metals are elements that fill the f orbitals.
Are representative metals and main group metals the same?
Yes, representative metals are also called main group metals.
Is Group 12 thought to be the representative metals?
Transition metals are commonly thought to be Group 12 elements; however, zinc (Zn), cadmium (Cd), and mercury (Hg) share some properties of both groups and many scientists believe they should be classified as representative metals.
Why are the s and p-blocks referred to as representative elements?
The elements of the “s” and “p” blocks are referred to as representative elements because their outer shells are not completely filled with electrons, and the elements achieve the closest inert gas configuration by losing, gaining, or sharing electrons.
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