MODERN PERIODIC TABLE OF ELEMENTS

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Q:What is periodic table?

Ans:The table in which all the elements are classified according to their properties is called periodic table. In this table elements are arranged in the increasing order of their atomic number.In this arrangement elements with similar properties fall under same vertical column The aim of this arrangement of elements into the tabular form is to make their study easier.

Q:What is periodicity?

Ans:The repetition in the properties of elements after certain regular intervals in the modern periodic table is called periodicity. It means when the elements are arranged in order of their increasing atomic numbers, the properties of the elements are repeated after certain regular intervals in the modern periodic table.

Q:What is Modern Periodic Law?

Ans:This law states that the physical and chemical properties of elements is a periodic function of their atomic numbers.

Q:What is the cause of periodicity?

Ans:The repetition of the same valence shell electronic configurations of the elements present in a group after certain regular intervals is the cause of periodicity.

Q :- What are magic numbers?

Ans:The electronic configurations of alkali metals are repeated after regular intervals of 2,8,8,18,18 and 32. These numbers are sometimes called magic numbers.

Modern Periodic Table

Q:Explain long form of modern periodic table in detail.

Ans:In 1921 Bohr constructed the long form of modern periodic table. For an easy and systematic study, the elements of the modern periodic table are classified into:

1.PERIODS

2.GROUPS

3.BLOCKS

1) PERIODS

The modern periodic table has been divided into seven horizontal rows called periods. The first, second and third periods are called short periods. They contain 2, 8 and 8 elements respectively .Fourth, fifth,sixth and seventh periods are called long periods .They contain 18, 18 ,32 and 32 elements respectively.

2) GROUPS

1. The modern periodic table has been divided into eighteen vertical columns called groups.
2. 1st group: Elements of this group are called alkali metals. This group includes H, Li,Na,K,Rb,Cs and Fr.
3. 2nd group:Elements of this group are called alkaline earth metals and includes Be, Mg, Ca, Sr, Ba and Ra.
4. 3rd to 12th groups:The elements from group 3rd to group 12th are known as transition elements.
5. 13th group:This group is also called boron family because boron is the first element of this group.It includes B,Al,Ga,In and Tl.
6. 14th group : This group is called carbon family. It includes C, Si, Ge, Sn and Pb.
7. 15th group:This group is also known as nitrogen family or pincogens. This group includes N, P, As, Sb and Bi.
8. 16th group :This group is known as oxygen family or chalcogens. It includes O, S, Se, Te and Po.
9. 17th group:The elements of this group are also called halogens . These are F, Cl, Br, I, and At.
10. 18th group:The elements of this group are known as inert gases or noble gases. These are He, Ne, Ar, Kr,Xe Rn.

3)BLOCKS

Elements in the modern periodic table have been divided into four blocks. This division is based upon the name of the orbital that receives the last electron. These blocks are called:

i) s-BLOCK

The elements whose last electron enters into the s orbital of the outermost shell are called s-block elements. This block contains elements of group-I and group-II.

ii) p-BLOCK

The elements whose last electron enters into the p-sub shell of the valence energy level are called p-block elements. This block contains elements from group number 13th to group number 18th .

Representative elements

The s-block and p-block elements are collectively known as representative elements.

iii)d-BLOCK

The elements whose last electron enters into the d-sub shell of the penultimate energy level are called d-block elements. This block contains elements from group 3rd to group 12th .

iv) f-BLOCK

The elements whose last electron enters into the f-sub shell of the ante-penultimate energy level are called f-block elements. or.The elements whose last electron enters into any one of the seven f-orbitals of the ante-penultimate shell are called f-block elements. This block consists of two series of elements.

1. Lanthanide

2. Actinide

These two series are placed at the bottom of the periodic table. Each series comprises fourteen elements. The first series is called Lanthanide and second series is known as Actinide. The f-block elements are also known as inner transition elements.

Q:- Why do elements in the same group have similar properties?

Ans:- Because they have similar outer shell electronic configurations.

Q:- Why atomic number is batter base for classification of elements than atomic mass?

Ans :Atomic mass is a nuclear property and it has very little effect on the physical and chemical properties of the elements . Atomic number is directly linked to the number of electrons present in the extra nuclear part of an atom. Physical and chemical properties depend upon the number of electrons. Therefore, atomic number is considered to be the better base for classification of elements.

CHARACTERISTICS:s-BLOCK

1. They are soft metals.
2. They have low melting and boiling points
3. They have low ionization energies.
4. They are highly reactive in nature.
5. They are electropositive in nature.
6. They show oxidation states of +1 and +2.
7. They form ionic compounds (except beryllium).
8. They impart characteristic colors to the flame (except Be & Mg).
9. They are strong reducing agents
10. They are good conductor of heat and electricity.

CHARACTERISTICS:p-BLOCK

1. They include both metals and non-metals.
2. They exist in all the three physical states.
3. Their ionization energies are higher than s-block elements.
4. They generally form covalent compounds.
5. Most of them show variable oxidation states.
6. Their oxidizing character increases from left to right in a period.
7. Reducing character increases from top to bottom in a group.
8. They possess higher values of Electronegativity.




CHARACTERISTICS:d-BLOCK

1. They are hard metals (except Hg).
2. They have high melting and boiling points.
3. They are good conductor of heat and electricity.
4. They show variable oxidation states.
5. They form colored compounds.
6. They from complex compounds.
7. Most of them are used as catalysts
8. They form ionic and covalent compounds.
9. Their IEs lie b/w s and p-block elements.
10. They also form alloys with other metals.

CHARACTERISTICS:f-BLOCK

1. They are heavy metals
2. They have high melting and boiling points
3. They show variable oxidation states.
4. They form complex compounds.
5. They form colored compounds
6. Almost half of them are radioactive in nature.
7. Most of them are paramagnetic in nature.
8. Most of them are synthetic.



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