Arrangement of Elements in Periodic Table

Why do we need to Classify Elements?

At present, 114 elements are known, and remembering every property of elements is difficult. So, to solve the problem, chemists tried to organize elements systematically.

Dmitri Mendeleev organized the elements in the order of atomic mass and general formulae of their oxides and hydrides in the form of a table called periodic table.

Disadvantages:

1. No fixed position for hydrogen.
2. No fixed position for isotopes.
3. Cobalt, whose mass is more than nickel, is placed before nickel.

Henry Mosely organized elements in the order of atomic number.

The law states that the chemical and physical properties of the elements repeat in a regular, periodic pattern when arranged according to their atomic number.

Arrangement of Elements in Periodic Table

In the periodic table, each element is placed in a separate box along with its atomic number and mass. The table has seven periods (horizontal rows) and 18 groups (vertical columns). The table is classified into three parts as metals, non-metals, and metalloids (shown in the red color box).

Classification of Periodic Table

1. Main Group Elements Or Representative Elements

a. GROUP 1 – ALKALI METALS

Physical properties: are soft, metallic (like the malleable, ductile, good conductor of electricity)

Chemical properties: highly reactive, react vigorously with water

b. GROUP 2 – ALKALINE EARTH METALS

Physical properties: are shiny and silvery white. They appear dull due to the formation of the oxide layer.

Chemical properties: are very reactive, less than alkali metals. They are not found free because of their high reactivity.

c. GROUP 13 – NITROGEN FAMILY

Physical properties: their densities are higher than group 2. They are electropositive in nature as they can lose electrons. They are also not found in a free state.

Chemical properties: they are reactive but less than groups 1 and 2. They react with oxygen to form a thin layer of oxide on the surface.

d. GROUP 14 – CARBON FAMILY

Physical properties: they are generally solids. Carbon and silicon are non-metals; germanium metalloid, tin, and lead are metals.

Chemical properties: can react with oxygen to form monoxide and dioxides.

e. GROUP 15 – PNICTOGENS

Physical properties: are polyatomic. Dinitrogen is a diatomic gas, while all others are solids. Nitrogen and phosphorus are non-metals; arsenic and antimony are metalloids; bismuth is a metal.

Chemical properties: React with hydrogen to form hydrides.

f. GROUP 16 – CHALCOGENS

Physical properties: Oxygen and sulfur are non-metals, selenium, and tellurium are metalloids, and polonium is a metal. Polonium is radioactive.

Chemical properties: React with hydrogen to form hydrides of the type H₂E.

g. GROUP 17 – HALOGENS

Physical properties: chlorine and fluorine are gases, bromine is liquid, and iodine is solid.

Chemical properties: are reactive in nature. Combine with hydrogen to form hydrogen halide.

h. GROUP 18 – NOBLE GAS

Physical properties: are colorless, tasteless, and odorless gases. They have low melting and boiling point because there is a weak dispersion force between the atoms.

Chemical properties: they are generally the least reactive in nature.

2. Transition Metals

The transition elements are situated in groups 3 to 12 of the periodic table.

1. These elements possess metallic properties (such as high tensile strength, ductility, malleability, high thermal and electrical conductivity, and metallic luster)
2. The exceptional cases are Zn, Cd, Hg, and Mn.
3. The transition metals (except Zn, Cd, and Hg) are very much hard
4. They have low volatility
5. Their melting and boiling points are high.
6. High electrical conductivity and thermal conductivity

3. Inner Transition Metals

1. It consists of two series, lanthanoids (the fourteen elements following lanthanum) and actinoids (the fourteen elements following actinium).
2. The lanthanoids resemble one another more directly than transition elements in any series.
3. Inner-transition elements (lanthanoids and actinoids) are placed in two rows separated from the main periodic table.

Applications

1. Uranium and plutonium are used in making nuclear weapons and in making explosives.
2. They are used in nuclear power plants.
3. They are used to produce lasers.
4. Samarium and lutetium are used in determining the age of the fossils and rocks.
5. They are used to make strong magnets.
6. They are widely used in making sunglasses.
7. They are used in destroying the particular targeted cells in the body.