Periodic properties ( types of bonds)

Why we study periodic properties

Here we will continue periodicity of a periodic table . In the last post we have seen the important concept of effective nuclear charge . Periodic properties is the main reason why we study periodic table. As we say elements are classified into different categories in periodic table because of its periodic properties.

Some of the elements have metallic properties so they are classified into generally in 's' and 'd block' and others which are following non-metallic character ,generally classified in 'p block'. And because of many other such properties the elements are categories into period, group and block ,etc. 

So we will study all the periodic properties of elements one by one and we will also see the effect due to effective nuclear charge .

1. ATOMIC RADIUS

Atomic radius of the elements is the distance from the center ( i.e central nucleus ) to the outermost shell where the probability of finding electron become zero . Here you might be confuse that what is probability of finding electron so don't worry we will learn in upcoming post . I will provide You link below after some time.

Types Of Atomic Radius :

1. Covalent radius 
2. Metallic radius 
3. Vander wall radius

I.  Covalent radius 

Hope you would know what is covalent bond otherwise we will see in Chemical Bonding . As we know in the formation of covalent bond is due to overlapping of orbitals . So half of the inter-nuclear distance between the two bonded atom is defined as covalent radius.

δ

Bond length is the inter nuclear distance as shown in figure. So covalent radius is the half of the bond length.

Covalent radius is generally applicable for non-metal or p-block element (except inert gas).

Ex. -- H₂ O₂ N₂ F₂ Cl₂

II. Metallic radius 

Metallic bond is the bonding formed between metals due to intermittent presence of valance electron. So metallic radius is half of the inter-molecular distance of two touching atom of metal . Metallic radius is always larger than covalent radius. Since metallic bond is property of metal so it is applicable for s-block , d-block, and f-block elements.

III. Vander Waal radius 

Vander-Waal radius is mainly property of inert gas due to formation of Vander-Waal bond. Due to large size of atom there will Vander-Waal force of attraction and that's why this type of bond formation is possible. It is a weak electrostatic force between molecules or atom / noble gas .

Note:  1.Wander-Waal radius is the largest radius .

           2.Generally Vander-Waal radius is two times of covalent radii.

VanderWall Radius  > metallic Radius > Covalent Radius 

General Trend of Atomic radius

• Left to right in the period atomic radius decreases because Z_eff (effective nuclear charge) increases in period as we seen earlier .

          Ex.  Li  > Be > B > C > N > O > F

• Inert gas have largest atomic radius in the period due to Wanderwaal radius .
• When we move top to bottom in the group atomic radius increases because the number of shell increases. Here point to be noted that size of atom increases not because of effective nuclear charge ,if you remember we have studied that in group there will not change in effective nuclear charge. So here size increases due to number of shell is increases .

          Ex.      B   2s² 2p¹

                     Al   3s²  3p¹

                     Ga   4s² 4p¹

                     In    5s²  5p¹

                     Th    6s²  6p¹

Irregular Trend in Periodic Table

• As we move from top to bottom in the Boron family  the atomic radius from Boron to Aluminium increases abnormally while from Al to Ga it remain almost constant .

           Why is this happen ...

   As we move from 'B' to 'Al' the atomic size increases abnormally due to strong screening effect of  'S' and  'P'  orbital .

               Z_eff   =  | Z - σ | 

As we move from 'Al'  to 'Ga' atomic size is almost constant due to poor screening effect of d-orbital .

Z_eff ↑  = Z- σ ↑ 

Note : This is applicable on  B- Family , C- Family and N- Family .

Lanthanide Contraction 

It is one of the most important concept in periodic properties . when we move from 4d series (5th peiod ,d-block) to 5d series (6th period , d-block) the atomic size remain almost constant due to poor screening effect of 5d and 4f orbital this phenomena is defined as "lanthanide contraction".

4d series :  Rb  Sr   Y    Zr   Nb  Mo   Tc   Ru   Rh   Pd   Ag   Cd   In   Sn   Sb   Te    I    Xe

5d Series :  Cs   Ba  La  Hf   Ta   W     Re   Os   Ir     Pt   Au   Hg   Tl   Pb    Bi   Po   At   Rn

Effect due to lanthanide contraction

Effect 1:            IIIB         IVB         VB         VIB

                           Sc             Ti             V           Cr

                            Y             Zr            Nb         Mo

                           La            Hf            Ta           W

Atomic radius of 4d series and 5d series are approximately equal 

i.e   Zr = Hf ,       Nb = Ta ,     Mo = W

    

Effect 2:  Inert pair effect 

P block elements are generally form co-valent bond so for this excitation of e- will happen .

But in the case of 6th period excitation will not possible due to lanthanide contraction ( more Z* ) and so that nucleus will attract e- with high magnitude . This is inert pair effect.

It is the non-participation of  's' orbital electron in bond formation due to more closer to nucleus and lanthanide contraction . Nucleus have more effective nuclear charge.

IIIA                                             IVA                                         VA 

B                                                   C                                            N

Al                                                 Si                                            P 

Ga                                                Ge                                           As

 

In                                                  Sn                                           Sb

Tl             Tl⁺  is stable                Pb         Pb²⁺  is stable           Bi         Bi³⁺  is stable 

IV. Ionic radius 

The size of cation is always smaller smaller than its neutral form. In cation, some of the electron is lesser than neutral form. 

Ex .        Na  >  Na⁺ ,      K  >  Na⁺

As the number of +ve charges increases atomic size decreases because due to less electron. 

 Ex .        Fe²⁺  >  Fe³⁺ 

              

As One of the most important concept related to isoelectronic species and is frequently asked in all competitive examinations.

Higher the atomic number lower the atomic radius.

Ex .        F^-  >  Na⁺  > Na⁺  > Mg²⁺  > Al³⁺

 Note :  H⁺ is the smallest cation while Cs⁺ is largest cation and H^-  is the smallest anion while I^- is the largest anion.         

what is periodicity

introduction:

Periodic table is design in such a way so that we can understand all the physical and chemical properties in a proper order . Elements having similar properties are placed either in same group or same period as well as.

Periodicity :

The repetition of physical and chemical properties after the regular time interval is defined as periodicity of periodic table. Basically it depends on many factor i.e screening effect,electron affinity and electronegativity etc.

Screening effect or Shielding effect

The phenomena of decrement in the force of attraction between the outer electron and nucleus because the nucleus and the valence shell electron due to inner electron is defined as screening effect or shielding effect.

effective nuclear charge

It is defined by slater
                                   

                                   Z* = Z - σ
here Z* is effective nucleus charge , Z is nuclear charge and σ is screening const or slater const .

The reduce force of attraction by the nucleus on the valence electron (see in above figure) is defined as effective nuclear force. It is discuss in term of charge so it is named as effective nuclear charge.

Calculation of screening effect of any element through following  slater rule:

• Arrange the orbital in the given form

             (1s) (2s 2p) (3s 3p) (3d) (4s 4p) (4d 4f)

• The amount of extent from which the force of attraction decreasing is named as screening constant (σ ) .
• The value of screening constant for the different shell are : -

         

Shell	(n-4)th	(n-3)th	(n-2)th	(n-1)th	nth
σ	1	1	1	0.85	0.35

Let's take some example to more understanding

Ex.     1.  Li ➝ 1s² 2s¹
                      σ = 2 x 0.85 = 1.7     so,  Z*= Z- σ = 3-1.7=1.3
  here we are finding screening const of last electron so we have not consider n^th  electron.
 Same things have done in upcoming example .

          ^{2. Na ➝}  1s²   2s² 2p6  3s¹
                           ↑          ↑        ↑
                       (n-2)     (n-1)    n

                  σ = 8 x 0.85 + 2 x 1 = 8.8

                so  Z*= 11-8.8 =  2.2

           ^{3. K ➝}  1s² 2s² 2p6     3s² 3p6     4s¹
                             ↑                  ↑
                         inner              (n-1)

                  σ = 8 x 0.85 + 2 x 1 + 1 x 0.35 = 9.15

                  so  Z*= 12-9.15 =  2.85


           ^{4. Mg ➝}  1s²   2s² 2p6  3s²
                             ↑          ↑        ↑
                         (n-2)     (n-1)    n

                  σ = 8 x 0.85 + 2 x 1 + 1 x 0.35 = 9.15

                  so  Z*= 12-9.15 =  2.85

           ^{5. Ca ➝}  1s²    2s² 2p6   3s² 3p6   4s²
                           ↑           ↑            ↑           ↑
                         (n-3)     (n-2)      (n-1)       n

                  σ = 8 x 0.85 + 10 x 1 + 2 x 0.35 = 17.15

                so  Z*= 20-17.15 =  2.85

let's try it

Find the screening constant and then effective nuclear charge for the last for the last e- of :
(a)  Zn       (b)  B     (c)   N

Check solution  for more clear :  

https://drive.google.com/open?id=1DX-f57Vg1l7FZStN7xwYK2SEWpKpwnYX

As you can see in above example of  Na , K and Ca ( which belongs to same group i.e 1st group ).
The Z* (Effective nuclear charge ) of all the elements are almost same .So we conclude a important note that there is no change in Z* in group .

Now take some example in the same period elements.

1. B = 1s²   2s² 2p¹
           ↑         ↑       
          n-1       n
 σ = 2 x 0.85 +  2 x 0.35 = 2.40
Z* = 5 - 2.40 = 2.6

2. C = 1s²   2s² 2p²
           ↑         ↑       
          n-1       n
 σ = 2 x 0.85 +  3 x 0.35 = 2.75
Z* = 6 - 2.75 = 3.25

3. N = 1s²   2s² 2p³
           ↑         ↑       
          n-1       n
 σ = 2 x 0.85 +  4 x 0.35 = 3.1
Z* = 7- 4 = 3.9

B   --    C    --    N    --    O           here consecutive difference = 0.65
↑           ↑           ↑            ↑
2.60    3.25     3.90        4.55   

so we get another important point

Note : In period ,Z* increases by 0.65 for each movement in period.

So we have seen how to find screening constant and effective nuclear charge for a particular elements . These concept are very important to understanding other periodic properties in the table.

Some of the important properties like lanthanide construction , we will see in upcoming post.

4.Periodic Table_d-block & f-block

#d-block elements

Here we will see the property of  d-block and f-block elements . As you have seen the elements are classified into block as their last electron enter the particular orbital. In the same way here if the last electron enter the d-orbital of penultimate shell ,then the elements belong to d-block.

d-block elements

IIIB	IVB	VB	VIB	VIIB	VIIIB			IB	IIB
--	--	--	--	--	VIIIB	IXB	XB	--	--
Sc	Ti	V	Cr	Mn	Fe	Co	Ni	Cu	Zn
Y	Zr	Nb	Mo	Tc	Ru	Rh	Pd	Ag	Cd
La	Hf	Ta	W	Re	Os	Ir	Pt	Au	Hg

Properies :

• The maximum capacity of d-orbital is 10. so there are 10 vertical column in d-block.
• There are 8 group in d-block starting from 'IIIB' and terminating on 'IIB'.
• d-block start with 3d-series of 4th -period.

            ( Sc ------ Zn )-------> 3d - series

            ( Y ------ Cd )-------> 4d - series

            ( La ------ hg )-------> 5d - series

            ( Ac ------ Radioactive element )-------> 6d - series

• All the d-block elements are 'hard - metal' due to strong metallic bond.
• d-block elements are involve in complex formation.

          Ex.  K₃[Fe(CN)₆] ,  [Ni(CN)₄]^2-.
Note : Complex -compound or salt don't loose their identity in aqueous solution. 

• General Electronic configuration : ( n-1 ) d^1-10 ns²

 3d    {   Sc      Ti       V        Cr       Mn        Fe       Co       Ni        Cu       Zn
         {
 4d    {    Y        Zr      Nb      Mo      Tc         Ru       Rh       Pd        Ag      Cd
         {
 5d    {    La       Hf      Ta      W         Re        Os       Ir          Pt        Au      Ag

• Oxidation number of d-block is variable and it can show maximum oxidation state of +8 for Osmium and Ruthenium.

             Ex.    Os⁺⁸ O₄

#f-block elements

If the last electron enter the f-orbital then the element belongs to f- block. The capacity of f-orbital is 14 and so there are 14 vertical column in f-block.
It derives from IIIB group of 6th period.

      

Properies :

• All the f- block element belongs to Group - IIIB.
• f-block elements belongs to Group- IIIB.
• f-block elements are similar in chemical property.
• These are present in two horizontal row named as -

1. Lanthanide  Ce (58) -----------------Lu (71)                                                                                                          Cerium                        Lutetium 
2. Actinide        Th (90) ---------------   Lr (103)

lanthanide Series :  

               Ce   Pr   Nd   Th  Pm  Sm   Eu   Gd    Tb   Dy   Ho   Er   Tm   Yb   Lu

Trick To Remember:--  सी  पर  नंद  था  Prime Minister  श्रीमती युरो जीडी टब्डी     हो   अरे Tm Yb का 

                                       Ce  Pr  Nd          Pm                     Sm    Eu   Gd   Tb Dy   Ho  Er  Tm   Yb
                                     किया    लुट

                                                 Lu

• General Electronic configuration ( Lanthanide Series ) : [Xe]4 f^1-14 5d^0-1 6s².

Ex..

₅₆Ba --> 1s²  2s²  2p⁶  3s²  3p⁶  4s²  3d¹⁰  4p⁶  5s²  4d¹⁰  5p⁶  6s².
₅₇la-->   1s²  2s²  2p⁶  3s²  3p⁶  4s²  3d¹⁰  4p⁶  5s²  4d¹⁰  5p⁶  6s²  5d1
₅₈Ce --> 1s²  2s²  2p⁶  3s²  3p⁶  4s²  3d¹⁰  4p⁶  5s²  4d¹⁰  5p⁶  6s²  5d¹   4f¹
₆₄Gd --> 1s²  2s²  2p⁶  3s²  3p⁶  4s²  3d¹⁰  4p⁶  5s²  4d¹⁰  5p⁶  6s²   5d¹   4f⁷ 

Note-   5d¹is possible for half filled and full filled f-orbital.

Actinide Series : 

        Th  Pa  U  Np  Pu  Am  Cm  Bk  Cf   Es  Fm  Md  No  Lr

Trick To Remember : -थापु          नापु Am Cm बाकी सब साफ इस Fm से मैडम No लटपट

                                    Th  Pa U Np Pu Am Cm   Bk        Cf    Es  Fm     Md   No   Lr

• All the element of f- block are metal with general oxidation number (+3).
• f-block metal are also involve in complex formation.

Long Form Of Periodic Table 

---

New Periodic Table was given by Rang ,Werner, Bohr and Burry ,etc so sometimes it is also called as Bohr ,Burry and Rang, Werner Periodic Table. They remove the drawback of modified periodic table of Mendeleev.
The complete periodic table was divided into horizontal row ( Period ) and vertical column ( Group ).
New periodic table contain 18 vertical column .Group VIIIB was divided into three vertical column named as 8, 9, 10th group.
pic:--

Nomenclature of elements for Z > 100

Nil =0           Pent = 5

Un = 1          Hex = 6

Bi =  2          Sept = 7                     Suffix -->  ium

tri =  3          Oct = 8

quad =4        Enn = 9

Ex.  Z = 104 ( Unq )

        Un + Nil + quad + ium  = Unnilquadium

Now you have to name the following ex:

 1. Z= 105  2. Z= 107   3. Z= 113   4. Z= 118

This nomenclature was introduced by IUPAC to stop the confusion because the elements after Atomic number = 92 is not natural but man-made (Artificial).

Before we going to the important topic periodicity ,we will see some important term and definition as you can see in the period table.

• Representative Elements : s & p black species are representative except VIIIA.
• Metalloids : Species which have both character ( metal and non metal ).

                             Ex.. B    Si    Ge    As   Sb    Te    Po

for Periodicity of periodic table please go through following link
..

3(a).Modern Periodic Table (s-block & p-block)

Classification on the basis of differentiating electron

Do you ever think why periodic table is classified into four block i.e s, p, d and f ?

Let's find it answer . In earlier we see the electronic configuration  of some element.Periodic table is classified into four block on the basis of last electron entering in the orbital and due to this orbital these elements are classified into that particular block.

Let's take some example to more clear

Here you can see in first example last electron of potassium is entering in s orbital and so it is classified as s-block element.Similarly Carbon is classified as p-block element,Chromium is classified as d-block and cerium is classified as f-block element (i.e lanthanide).

# s-block element : 

If the last electron enter into the s-orbital then the element belongs to s-block as you saw in the above example.As the capacity of s-orbital is 2,there are two vertical column in s-block. since upto only 2 electron will insert in s-orbital ,so there are only two elements insert in vertical column.

                       IA             IIA

                        H              Be                    *IA is named as alkali metal whereas IIA is named as 

                        Li             Mg                      alkaline earth metal.

                        Na            Ca

                        K              Sr

                        Rb             Ba

                        Cs             Ra

                        Fr              

→General electronic configuration is ns¹ ns².

⇢General oxidation state for group-1 is '+1' and group-2 is '+2'.
Here important point to be noted is general oxidation state mean the stable oxidation state.
→s-block elements are electro-positive in nature and they are named as soft-metal ( due to weak metallic bond ).
→s- block element have low melting and boiling point.
we will see the more property related with s-block element in upcoming blog.

# p-block element :

If the large electron enter into the p-orbital ,then the element belong to p-block.

      13                    14                     15                    16                     17                   18

IIIA	IVA	VA	VIA	VIIA	0
B Boron	C Carbon	N Nitrogen	O  Oxygen	F  fluorine	Ne Neon
Al Aluminum	Si  Silicon	P Phosphorous	S Sulfur	Cl Chlorine	Ar  Argon
Ga Gallium	Ge  Germanium	As  Arsenic	Se Selenium	Br Bromine	Kr Krypton
In Indium	Sn     Tin	Sb Antimony	Te tellurium	I Iodine	Xe Xenon
Tl Thallium	Pb Lead	Bi Bismuth	Po Polonium	At Astatine	Rn Radon

• The maximum capacity of  p-orbital is 6. So there are 6 group in p-block classification and there are six electron in outermost orbit of 0th-group element.
• General electronic configuration is ns²np^1-6 .

            Ex.         B                C              N               O                 Cl               Ne    

                       2s² 2p¹      2s² 2p²      2s² 2p³      2s² 2p⁴         2s² 2p⁵       2s² 2p⁶.

• Oxidation State : Oxidation number of p-block varies from 'n' to ( n-8 ) ,where 'n' is no. of valance electron. 

          Ex.             B                C                 N                    O                  P
                      [+3 to -5]    [+4 to -4]      [+5 to -3]       [+6 to -2]       [+7 to -1]

Note :

•  In case of halogen (group-VIIA or 17) oxidation number is +7 to -1 but it is not applicable for  'F' due to absence of d-orbital.

          See the electronic configuration of F (At no. 9)--> 1s² 2s² 2p⁵  due to absence of d- orbital                   the oxidation number is 0 to -1 only.
           for more detail to understand the concept of oxidation go through the following link :         

• Oxidation number of oxygen varies from -2 to +2.

             O --> 2s² 2p⁴
           for peroxide -->  H₂ O₂                 H⁺¹  --  O^-1 --  O^-1  --  H⁺¹.
           for superoxide --> O₂^-1...         Oxidation = -1/2

• Nitrogen can exhibits '+5' oxidation number only in case of HNO₃ but it is not general oxidation number because 'N' can't form 5-bond.

Hope you know how to find  oxidation number otherwise we will see in more detail in upcoming blog.Don't be nervous we have a trick to finding oxidation state, just wait.

Now we will see some of the important definition

 ✱ Lower -Oxidation number : Oxidation number due to the e- of  'p' orbital in the valence shell.

Ex.       B          C           N           O             F

          +1          +2          +3          +4           +5   ------> Due to p-orbital 

✱ Maximum-Oxidation number :   Oxidation number due to the e- of  's' and  p-orbital.

Ex.         B          C           N           O             F

             +3         +4          +5         +6            +7

✱ Minimum-Oxidation number :  Number of electron gained for completing the octet.
       
                           Minimum oxidation state = n-8

Hope you 're understanding the concept ,if you have any doubt don't hesitate to write in comment section.
                 Thanks..........

2.Modern periodic table

Modified Periodic Table of Mendeleev's   

or Modern Periodic Table

Up to here we see the basic classification of periodic table and one of the most important classification Mendeleev's classification which play important to role in the periodic classification.

Basically Mendeleev gives the basic idea to classified the elements.

Modern Periodic law: According to modern periodic law the physical and chemical property of the elements are the periodic function of atomic number.

Important features of modified Periodic table

1. Complete Periodic table was classified in horizontal row (i.e period) and vertical (i.e group).
2. All the group was divided into sub group 'A' and 'B'.
3. A new vertical column was added and named as 'zeroth' group ( consist of inert gases).
4. The repetition in the property will start according to these number.                                                       2 ,  8 ,  8 ,  18 ,  18 ,  32
5. Lanthanide and actinide are separate from the main periodic table and named as inner-transition element.
6. Complete periodic table was classified into 7 period.

•  1st period --> very short period (2)   
•  2nd period--> short period (8)      
•  3rd period--> short period (8)  
•  4th period--> long period (18) 
•  5th period--> long period (18)       
•  6th period --> longest period(32)
•  7th period --> longest period (32) or incomplete period   

Drawback of Moseley's periodic table

1. Position of Hydrogen: same as Mendeleev's periodic table, Moseley's periodic table also could not give the exact position of hydrogen.
2. Elements having different property are placed together .                                                               for example : alkali-metal with (Cu,Ag,Au)
3. Similar element are placed separately .                                                                                      for example :  Pb and Ba
4. No explanation about the position of lanthanide and actinides ( inner transition element).
5. No explanation about the position of metal and non metal.
6. No explanation about the position of 12 transition element elements in the group-VIII.                EX--   Fe ,   Co ,   Ni                                                                                                                         Os ,   Ir  ,    Pt

These are the common drawback that are not define in the Moseley's P.T(i.e modern Periodic).Some of the other common drawback is also available that are not given till now.

Classification of P.T on the basis of electronic configuration

Now we will see how to configure the elements on the basis of their orbit i.e electronic configuration.

Electronic configuration of an elements gives the distribution of electron in orbit of an atom.

We all are familiar with s, p, d & f .

For detail understanding of electronic configuration and distribution of elements please go through following link:

Hope you will be understand it ,now we are coming to point .

Before going further see some example of electronic configuration of elements---

some example of electronic configuration     

some important definition 

• Inert Gas : Those element whose outermost shell is completely  filled. These are the group-VIII elements. Ex.  He ,  Ne ,  Ar ,  Kr ,  Xe ,  Rn                                                                                     General electronic conf. -->  ns²np⁶     

• Representative element : Those element whose outermost shell is incomplete are named as representative element.These are commonly p-block elements.                                                                   General electronic conf. -->  ns¹ or ns² np^1-6                                                     

              Ex.   Mg        Al               Si                  P               S                 Cl                                                                     3s²     3s² 3p¹       3s² 2p²        3s² 2p³       3s² 2p⁴       3s² 2p⁵

• Transition metal: Those metal whose outermost shell is incomplete as well as penultimate shell is incomplete.Here penultimate shell means shell before outermost shell.             Generally d-block elements are  known as transition  metal.  

                                   

Structure_of_atom

                                                               

                            General electronic conf. -->  (n-1)d^1-9 or ns²                                                                                Ex.

• Inner transition metal :  Those metal whose outermost shell is incomplete as well as penultimate and before penultimate is also incomplete.As you can see in the above picture and concentrate the shell before penultimate shell.

          General electronic conf. -->  (n-2)f^1-14  (n-1)d^0-1  ns²

 ↗                    ↑                 ↖   

                             before penultimate         penultimate     outermost

These are mainly f-block elements i.e lanthanide  and actinide.

go further to continue through following link :
              https://shrischool.blogspot.com/2020/05/3modern-periodic-table-s-blockp-blockd.html