• Valence Shell: nth shell, 1st outer shell


• Penultimate Shell: (n-1)th shell, 2nd outer shell


• Pre-penultimate shell: (n-2)nd shell, 3rd outer shell

• First person to classify elements on basis of their characteristics


• Triad law


• Formed groups of 3 elements each


• Based on Atomic Mass


• Didn't classified all elements (drawback)

#2 Newlands:

• Octave Law


• Characteristics of every eighth element is similar to that of the first element


• Based on Atomic Mass


• Worked fine only upto Calcium, i.e., valid only for lighter elements (drawback)

#3 Lothar Meyer:

• Based on Atomic Mass


• The elements having similar properties will occupy the same position in curve


• Halogens are the ascending part of the curve


• The atomic volume of the elements in a period initially decreases and then increases

#4 Mendeleev:

• Based on Atomic Mass


• First person to classify elements in form of a table; later known as Periodic table


• Predicted occurrence of 3 elements and left space for them in the periodic table:
   
  • Eka-Boron: After Boron: Scandium
  
  
  • Eka-Aluminium: After Aluminium: Gallium
  
  
  • Eka-Silicon: After Silicon: Germanium
  
  
  
  
• Horizontal: Periods, & Vertical: Groups


• Arranged elements in increasing order of Atomic Mass


• Placed some heavier elements before some lighter elements (drawback); these are known as Mendeleev's Anomalous Pairs


• Anomalous Pairs: Ar & K, Te & I, Th & Pa, Co & Ni [Aamir Khan Teri Ichcha Thandi Pepsi Kyon Nahi]

#5 Modern Periodic Table:

• Given by Moseley


• Based on Atomic Number


• 18 Groups and 7 Periods


• Long Form of Periodic Table: When elements are arranged in modern periodic table in the form of electronic configuration, then it is called L.F.P.T - Given by Rang, Burner & Burrey



# On the basis of electronic configuration, elements are of 3 types:

• Representive/Normal elements


• Transition elements


• Inner-transition elements


• Representive elements: s & p-block elements, (except group 18) - Valence shell is incomplete


• Transition elements: d-block elements - Penultimate shell is incomplete


• Inner-Transition elements: f-block elements - Penultimate & Pre-Penultimate shells are incomplete

# s-block:

Those elements in which the last electron enters into the s-subshell of the valence shell are known as s-block elements.

• Position of s-block elements in L.F.P.T: Left hand side, 1st Period, and contains group 1 & 2


• g.e.c.f: ns1-2

# p-block:

Those elements in which the last electron enters into the p-subshell of the valence shell are known as p-block elements.

• Position of p-block elements in L.F.P.T: Right hand side, starts from 1st period, spans from 13th to 18th group


• g.e.c.f: ns2 np1-6

• Last electron enters into the d-subshell of penultimate shell.


• G.E.C.F: [noble gas] (n-1)d1-10 ns1-2


• Position: Middle, Starts from 4th Period & contains Group 3rd to 12th


• n = 4: 3d Series: Scandium to Zinc


• n = 5: 4d Series: Yttrium to Cadmium


• n = 6: 5d Series: Lanthanum → Lanthamoids → Hafnium → Mercury


• n = 7: 6d Series: Actinium → Actinoids → Rutherfordium → Copernicium


• 

• G.E.C.F: [noble gas] (n-2)f1-14 (n-1)d0-1 ns2


• Pre-Penultimate (n-2) and Penultimate (n-1) shells are incomplete


• Last electron enters into f-subshell of Pre-Penultimate shell → f-block elements


• Position in L.F.P.T: Starts from 6th Period & contains 3rd (or IIIB) Group


• n = 6: 4f Series: 1st Inner-transition series: Lanthamoids: Cerium → Lutetium


• n = 7: 5f Series: 2nd Inner-transition series: Actinoids: Thorium → Lawrencium


• 

# For Block:

• ns → s-block


• ns np → p-block


• (n-2)f (n-1)d ns → if d0-1: f-block; else d-block

# For Period:

• Period number = n (max. value of 'n')
  • Exception: Palladium

# For Group:

• s-block: nsx → Group number: x


• p-block: nsx npy → Group number: 10 + x + y


• d-block: (n-1)dz nsx → Group number: z + x


• f-block: Always 3rd Group only

# Along a Period:

• Atomic number increases one by one


• Number of electrons increases one by one


• Number of protons increases one by one


• Number of shells remain constant


• Number of valence electrons increases one by one


• Number of electrons between nucleus & valence shell remains constant

# Down a Group:

• Atomic number increases rapidly


• Number of electrons increases rapidly


• Number of protons increases rapidly


• Number of shells increases one by one


• Number of valence electrons remain constant


• Number of electrons between nucleus & valence shell increase rapidly

The overall force of attraction of nucleus on the valence shell electron is known as Effective Nuclear Charge.

• Zeff = Z - (sigma)

• It is exerted by those electrons which are present between nucleus & valence-shell.


• Screening effect along Period: Constant or decreases due to number of electrons between Nucleus & Valence-shell.


• Screening effect down a group: Increases due to increase in number of electrons between Nucleus & Valence-shell.

• It is the distance between Nucleus and Valence-shell in ground state of the atom

# Types of Atomic Radii:

1. Metallic Radius (for metals): 2r = Intermolecular distance = Bondlength rm = Metallic Bondlength / 2


2. Co-valent Radius (for non-metals): rcov = CVBL / 2


3. Vanderwalls Radius (for noble gases): rv


4. rv > rm > rcov

# Factors affecting atomic radius:

• radius ∝ (number of shells)


• radius ∝ (1/Zeff)


• screening effect: r ∝ (σ)


• nature of bonding: rv > rm > rc

Periodicity:

• Along a Period: Atomic radius decreases due to increase in Zeff, but radius decreases upto halogens & is maximum in Noble gases


• Down a Group: Atomic radius increases due to decrease in Zeff

• Also known as Ionization Potential & Ionization Enthalpy


• Defined for 1 mole of atoms in ground & gaseous state


• Definition: Amount of energy required to remove an electron from the valence-shell of an atom present in ground & gaseous state


• Bond breaking is an Endothermic process

# Factors affecting Ionization Energy:

• number of shells: I. E. ∝ (1 / number of shells)


• Zeff: I. E. ∝ (Zeff)


• screening effect: I. E. ∝ (1 / σ)


• stability of sub-shells: I. E. ∝ (stability of half/fullfilled sub-shells)
  • stability: p6 > d10 > p3 > d5

# Periodicity:

• Along a Period: I. E. increases due to increase in Zeff


• Down a Group: I. E. decreases due to decrease in Zeff


• 


• Maximum I. E.: Noble Gases


• Minimum I. E.: Alkali Metals


• I. E1 of Alkali Earth Metals > I. E1 of Boron family


• I. E1 of Nitrogen family > I. E1 of Oxygen family

# Successive Ionization Energy:

• I. E1 < I. E2 < I. E3 … < I. En

• Defined for 1 mole of Gaseous atoms in ground state


• Definition: It is the amount of energy released when an electron is added in the Valence-shell of an atom present in ground & gaseous state

# Factors affecting Electron Affinity:

• number of shells: E.A. ∝ (1 / number of shells)


• Zeff: E. A. ∝ (Zeff)


• screening effect: E. A. ∝ (1 / Σ effect)


• nature of sub-shells: fullfilled: E. A. = 0 & halffilled: E. A. (nearly) = 0

# Periodicity:

• Along a Period: Increases due to increase in Zeff


• Down a group: Decreases due to decrease in Zeff


• Ex.: Li < B < C < O < F
  [ Max. E. A. → Halogens ]


• On going down a group E. A. decreases but in non-metals (15th, 16th, and 17th group), 3rd period elements' E. A. is greater than that of 2nd period elements due to small size & more valence electrons. So, more repulsion occurs on new in-coming electron


• Chlorine has the highest electron affinity

• Relative property


• Bonded property


• Definition: The capacity to attract the bonded electrons by an atom in a molecule is called Electronegativity

# Factors affecting E. N.:

• number of shells: E. N. ∝ (1 / number of shells)


• Zeff: E. N. ∝ (Zeff)


• screening effect: E. N. ∝ (1 / Σ effect)


• oxidation state: E. N. ∝ (Oxidation number)


• hybridization: E. N. ∝ (% of s-character), E. N. ∝ (1 / Hybridization), sp > sp2 > sp3

# Periodic Trends:

• Along a Period: Electronegativity increases due to increase in Zeff


• Down a Group: Electronegativity decreases due to decrease in Zeff


• Most electronegative atom: Fluorine

# Polarizing Power (Φcation): (only for cations) (Ionic Potential)

• Definition: The capacity to polarize the anion is called polarization
• Φcation ∝ (Charge / Size)


• Φcation ∝ (Hydrational ion)


• Φcation ∝ (Hydra-energy)


• Φcation ∝ (Size of Hydrated Cation)


• Φcation ∝ (1 / Ionic Mobility)