Classification of periodic table presentation

 

Classification Of Periodic Table 

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The objective of learning periodic TABLE

1.It enables us to learn the properties of a large number of elements, classification of similar elements having identical properties into groups which are required for time-saving & comprehensive study 

2.Periodic table is the most basic   concept in organic chemistry

3.We can easily remember

Valency of elements

Atomic mass & atomic Number

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Au-79.           Ge 32.                  Fe 26

4.Chemical properties of an Element 

5.How modern periodic table evolved 

Q.What is the periodic table 

The periodic table is a chart in which various elements are arranged such that similar elements are grouped together.

In 1800, there were only 31 known elements. By 1865, their number became 63. Now 118 By 2016, Now As different elements were being discovered, scientists gathered more and more information about the properties of these elements. They found it difficult to organize all that was known about the elements. They started looking for some pattern in their properties, on the basis of which they could study such a large number of elements with a History of classification

History of classification 

Metals & non metals 

The first attempt was to divide among metals & non-metals 

This division became a failure because some non-metals exhibit metallic properties & vice versa 

Example: 

1.iodine is a non-metal but exhibits a metallic lustre 

 2.mercury is metal but exists as a liquid 

So now this became failer

2nd attempt  Now on the basis of valency 

In this try elements having the same valency were put into the same group.

But unfortunately 😔 this became a failure as few didn’t satisfy 

Example: elements having the same valency had different chemical properties like Na,Cl

3rd attempt – Doberenier’s triads 

In 1817, Johann Wolfgang Dobereiner, a German chemist.     Dobreneir arranged the elements in order of increasing atomic weight. He saw that certain groups of three elements called the  “Triads “ had almost similar properties.

Hence the three elements are arranged such that the atomic mass of the middle element is the arithmetic mean of the other two elements

           (a triad of Elements with atomic mass )

              Eg: Li.        Na.       K.                   

                    7          23       39                      Mass of Na  7+39/2=23    

This classification failed because all the elements did not come into the triad form due to huge atomic mass difference

Limitations:

„ Dobereiner could identify only three triads from the elements known at that time and all elements could not be classified in the form of triads.

„ The law was not applicable to elements having very low and very high atomic mass. 

4th attempt – newlands law of octaves 

In 1866, John Newlands arranged 56 known elements in the increasing order of their atomic mass.     While arranging elements in the order of increasing atomic mass. Newland found that the right Element is similar in properties to the first one like the octave on a musical scale.

Eg.  Li.    Be.   B.   C.   N.    O.  F

.     Na.  Mg. Al.   Si.   P.    S.   Cl

.      K.     Ca

.      

The first element li & the eighth element Na are similar in properties . Newland could classify elements up to calcium in the way .as more & more new elements were discovered,they could not be filled into the octave structure

Limitations:

™ There are instances of two elements being fitted into the same slot, e.g. cobalt and nickel 

 Some elements, totally dissimilar in their properties, were fitted into the same group. (Arrangement of Co, Ni, Pd, Pt and row of halogens)

™ The law of octaves was not valid for elements that had atomic masses higher than that of calcium.

™ Newlands’ table was restricted to only 56 elements and did not leave any room for new elements.

™ The Discovery of inert gases (Neon. Argon….) at a later stage made the 9th element similar to the first one. Eg: Neon Fluorine 

and Sodium

™5th attempt Mendeleev's periodic table 

According to this classification, the physical & chemical properties of elements are periodic functions of their atomic weight. It was proposed by Dl Mendeleev in 1869

Features of this classification:

1. There are seven periods .horizontal rows are called periods 

2. There are right groups & each group is divided into two A & b subgroups .vertical columns are called groups.

3. Vacant spaces in between the tabular arrangement for the undiscovered elements.

It was noticed that certain elements could not be placed in their proper groups in this manner. The reason for this was wrongly determined atomic masses. Consequently, those wrong atomic masses were corrected. Eg: The atomic mass of beryllium was known to be 14. Mendeleev reassessed it as 9 and assigned beryllium a proper place.

™ Columns were left vacant for elements that were not known at that time and their properties also were predicted. This gave me motivation to experiment in Chemistry. Eg: Mendeleev gave names Eka Aluminium and Eka Silicon to those elements which were to be placed below Aluminium and Silicon respectively in the periodic table and predicted their properties. The discovery of Germanium later on, during his lifetime, proved him correct.

(b) Limitations:

™ Elements with a large differences in properties were included in the same group. Eg: Hard metals like copper (Cu) and silver (Ag) were included along with soft metals like sodium (Na) and potassium (K)

™ No proper position could be given to the element hydrogen. Non-metallic hydrogen was placed along with metals like lithium (Li), sodium (Na) and potassium (K).

™ The increasing order of atomic mass was not strictly followed throughout.  Eg. Co & Ni, Te & I.

™ No place for isotopes in the periodic table.

Successful attempt – the modern periodic law

according to this law, the physical & chemical properties of elements are periodic functions of their atomic numbers .this was given by Henry Moseley in the year 1913. 

Salient features of the long term the periodic table

„ All the elements are arranged in the increasing order of their atomic number.

„ The horizontal rows are called periods. There are seven periods in the periodic table.

„ The elements are placed in periods based on the number of shells in their atoms.

„ Vertical columns in the periodic table starting from top to bottom are called groups. There are 18 groups in the periodic table.

„ Based on the physical and chemical properties of elements, they are grouped into various families.

placed in the same group1. There are seven periods  .the number of elements present in each period is 

1st period – 2 elements.          4th period-18 elements.      

2nd period -8 elements.           5th period – 18 element

3rd period-8 elements             6th period- 32elements 

7th period - incomplete

Table 12.5 Groups in the modern periodic table

Group Families

1                  Alkali metals

2                 Alkaline earth metals

3 to 12        Transition metals

13               Boron Family

14               Carbon Family

15               Nitrogen Family

16               Oxygen Family (or) Chalcogen Family

17               Halogens

             Noble gases

Based on the arrangement of electrons in subshells, the elements of the periodic table are classified into four blocks namely s, p, 

d and f blocks.

(1) s-block Elements: It includes group 1 (alkali metals) and group 2 (alkaline earth metals) elements. They are also called representative elements. The elements of group 1 (except hydrogen) are metals. They react with water to form solutions that change the colour of a litmus paper from red to blue. These solutions are said to be highly alkaline or basic. Hence they are called alkali metals.  The elements of group 2 are also metals. They combine with oxygen to form oxides, formerly called 'earth', and these oxides produce alkaline solutions when they are dissolved in water. Hence, these elements are 

called alkaline earth metals.

2 )  p-Block Elements: These elements are in groups 13 to 18 in the periodic table. They include boron, carbon, nitrogen, oxygen, fluorine families in addition to noble gases (except helium). They are also called representative elements. The p-block is home to the biggest variety of elements and is the only block that contains all three types of elements: metals, nonmetals, and metalloids. 

(3) d-Block Elements: It includes group 3 to group 12 elements. They are found in the centre of the periodic table. Their properties are intermediate to that of s block and p block elements and so they are called transition elements.

(4) f – Block Elements: It includes 14 elements after (Lanthanum) La (57), called Lanthanoides and 14 elements after (Actinium) Ac (89), called Actinoides. They are placed at the bottom of the periodic table. They are also called inner 

Transition elements.

  

Advantages of modern  periodic table

1 ) easily remembrance of valencies of each element without knowing their atomic number 

                                 valencies

            group 1         +1

            group 2         +2

            group13      +3

            group 14      4

            group 15       3-

             group 16       2- 

             group 17         1-

              group 18        0  ( noble gases )

NOTE: 

GROUP 3 TO GROUP 12 BELONG TO TRANSITION METALS  & HAVE VARIABLE VALENCIES 

Separates Metals and Non-Metals:

Note; phosphorus is the only exception here since its valence

Is 3,5 

METALLIC & NON METTALIC CHARACTER

(+ve) (cation )        (-ve) (anion)

In period:   as we move from left to 

Right the metallic character

(Electeropositivity) of elements decreases

But the non-metallic character (electronegative) increases.  In middle, we have metalloids that exhibit both properties.

Metalloids BATSGAP

       B: BORON A: ANTIMONY T : TELLURIUM S: SILICON G: GERMANIUM 

A: ARSENIC P: POLONIUM 

2) In group: as we move down the metallic character increases & non-metallic character decreases 

 ATOMIC SIZE 

ATOMIC RADIUS: defined as the distance between the nucleus & outermost shell

Where electrons are present 

The atomic radius of an atom is determined by the following  radii

Ionic radius: it is the radius of the carbonic or an ionic sphere, which is present in the crystal of an ionic compound, surrounded by oppositely charged ions. IF  an atom A forms  A+ & A-

       Radius of A+ < Radius of A   < Radius of A- 

FACTORS AFFECTING IONIC RADII 

 1 Charge: -    Radius of Cation decreases with an increase in the magnitude of charge & that of anion increases with an increase in negative charge. 

Eg:  R fe3+ <R<Fe 2+ &          R o-1 <R o 2-

2) Nuclear charge: with an increase in nuclear charge (positive charge ), the radius of cations as well as a ions decreases

3)z/e ratio(z is atomic number or nuclear charge and e is total number of electrons .for isoelectronic species the z/e ratio lower higher the ionic radius

Eg:1)Fecl2>Fecl3                                   .

2)caf2<cao(f-1<o2-)

3) O2-  >F-   >na+> mg+2     (isoelectronic)

   8/10  9/10 11/10 12/10

 Note: The atomic radius decreases along       the period but the inert gases have the maximum radius in a period

TRENDS (FOR ATOMIC RADII)

1) IN PERIOD:  on moving from left to right,the atomic size decreases 

2) IN GROUP : On moving from top to bottom,the atomic size increases

Alkali metals  (group 1 )      1.li      2.Na      3.k     4.Rb      5 .Cs        6 fr                                                                    

mnemonics: Little naughty Krishna rules his  close   Friends 

1. They dissolve in water to form oxides          eg : li + h20= li oh + h2

2. They are so soft that they can be cut with a knife & Lustrous

3.They are most reactive.       

4.They all have valency as 1.

5. Low melting point

6.Conduct electricity 

7. sodium & potassium are so abundant that they are among the top 10 on the earth’s surface 

note: hydrogen is not alkali metal as it’s non-metal

2.Alkali earth metals

.   Be. Mg ca Sr ba a

Mnemonics : beans mango carrot sambar

.They are reactive, 

electropositive, 

divalent metals, and 

they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure.[2]

When they form oxides  they become basic thermally stable & do not even melt at high temperature hence these are called alkali earth metals

Abundance order in earth

    calcium > magnesium >barium > strontium > beryllium

7. These elements can be found in the form of  Oxides sulphate Carbonated & Halifax

Minerals of alkaline earth metals

             ELEMENT                mineral

1) beryllium                              :chrysoberyl , beryl                                                    ,phenacite

2) Magnesium                           : magnesite

3) Calcium                                : Limestone ,                                                              dolomite, gypsum,                                                      Marble,                                                                   anhydride,

                                                   fluorapatite 

4) Strontium               :              Celestite ,                                                                     strontianite 

5)Barium mineral:                   heavy spar ,witherite                                                 , Barytes

6) Radium                               : pitch blend ,                                                             carnotite 

                        

3) TRANSITION METALS 

  

The IUPAC definition[1] defines a transition metal as "an element whose atom has a partially filled d sub-shell, or which can give rise to cations with an incomplete d sub-shell".

Example :  element Titanium :  1s^2  2s^2 2p^6 3s^2 3p^6 4s^2 3d^2

                                                      So this forms cation to form 

 

Many scientists describe a "transition metal" as any element in the d-block of the periodic table, which includes groups 3 to 12 on the periodic table.[2][3] In actual practice, the f-block lanthanide and actinide series are also considered transition metals and are called "inner transition metals".

PROPERTIES  

Ionisation energy:

                         Ionisation energy is the minimum energy required to remove an electron from an isolated gaseous atom in its ground state to form a cation. It is otherwise called ionisation enthalpy. It is measured in kJ/mol

Higher the ionisation energy, it is more difficult to 

remove the electron

As the atomic size decreases from left to right in a period, more energy is required to remove the electrons. So, the ionisation energy increases along the period

Down the group, the atomic size increases and hence the valence

electrons are loosely bound. They require relatively less energy for the removal. Thus, ionisation energy decreases down the group in the periodic table. 

Electron affinity :- 

Electron affinity is the amount of energy released when an isolated gaseous atom gains an electron to form its anion. It is also measured in kJ/mol and represented by the 

following equation:

A(g) + e– → A–(g) + Energy 

Cl(g) + e– → Cl–(g) + energy

Like ionisation energy, electron affinity also increases from left to right in a period and decreases from top to bottom in a group.

Electronegativity :

Electronegativity of an element is the measure of the tendency of its atom to attract the shared pair of electrons towards itself in a covalent 

bond.

Electronegativity is based on various experimental data such as bond energy, ionization potential, electron affinity, etc.

Pauling scale is the widely used scale to determine the electronegativity, which in turn predicts the nature of bonding (ionic or covalent) between the atoms in a molecule

Electronegativity of some of the elements are given below 

F = 4.0, Cl = 3.0, Br = 2.8, I = 2.5, H = 2.1, Na = 1

If the difference in electronegativity between two elements is 1.7, the bond has 50% ionic character and 50% covalent character.

If the difference is less than 1.7, the bond is considered to be more covalent. If the difference is greater than 1.7, the 

bond is considered to be more ionic

Along the period, from left to right in the periodic table, the electronegativity increases because of the increase in the nuclear charge which in turn attracts the electrons more strongly.

On moving down a group, the electronegativity of the elements decreases because of the 

increased number of valence shells.

Lothar meyer arrangements

In 1869 lother Meyer A german chemist Studied the physical properties Of various elements 

In 1864, he published the first version of his periodic table through his book Die moderne Theorien der Chemie. 

it is clear that he not only ordered the elements with increasing atomic weights but also grouped them according to their valencies. The valence of an element is the combining power of the element with other elements. For example, the elements of the first column—C, Si, Sn, Pb—combine with hydrogen to form tetrahydride—CH4, SiH4, SnH4, PbH4. Thus, their valency is 4. Similarly, N, O, F, Na, Mg and other elements combine to form NH3, H2O, HF, NaH, MgH2… The grouping of elements based on their valency is the grouping them based on their chemical properties

Meyer plotted the graph of the atomic volume (molar volume) vs atomic weight. He noticed a series of maxima and minima. The most electropositive elements (Li, Na, K…) were observed at the peaks while the electronegative elements occurred at the ascent of the peaks.

all the elements between two consecutive maxima belong to the same period in the modern periodic table. For example, Li, Be, B, C, N, O, and F are placed in period 2. The trend in the chart depicts the periodicity of the elements

He published the finalized version of his periodic table in 1870. In this table, he incorporated additional elements, particularly transition metals known at that time. The table was divided into nine groups. This table was the transpose of his 1964's table, i.e., the rows were turned into columns and the columns into the rows

Question Time :

Questions Part A

1)arrange the following in decreasing value of 1st ionization energy 

C N. OF

2), arrange the following in decreasing ionic radio 

Cl-.   S2-.  K+ ca2+

3)The middle element of the dernier triad containing lithium & potassium is 

A)Arsenic B)bromine C)sodium D)strontium 

4)Which of the following element is most electropositive 

A)H b)mg c)ca D)si 

5)Elements of group 16 are also called 

A)Halogens B)noble gases C)chalcogens D)alkaline earth metals

.Hots(more than one correct )

1)which one of the following is a rare earth metal 

A)Scandium B)yttrium C)copper D) indium 

2)F block elements are generally ____ elements 

A)Rare earth B)radioactive C)catalytic D)non radioactive

3)Which of the following has the smallest size 

A)Ne b)o2- c)f- d)na+

4)What would be the atomic number of the next halogen element if discovered in future 

A)119 b)115 c)117 d)121

5)In the ground state Each atom of an element has two valence electrons this element has lower  first ionization energy than calcium  Location of the element in the periodic table is 

a)Group 3 period 5 b)group 2 period 5 c)group 2 period 3 d)group 3 period 3

Solution Pat A 

1. legislation energy increases along the period. SoF>N>O>c

 2)More negative charge is greater than less negative charge Less positive charge is greater than more positive charge So $2->cl->k+>ca2+ 3 Sodium

 4)A)H Electropositivity decreases along the period Electropositivity increases along the group These have opposite of Electropositivity

 5 C) chalcogens

1) A& B ARR CORRECT

2 abc

3}Ne 62-f- na+

p2-f-ne>nat

4)5 Extra stability of half-filled p orbitals

5B)group 2 period 5

EMBEDDED PRESENTATION OF CLASSIFICATION OS PERIODIC TABLE: