Periodic Table

Question 1

Classification by Proust

Answer 1

• every element is an aggregation of hydrogen atoms
• properties are integral multiples of the properties of hydrogen

Question 2

Lavoisier

Answer 2

• Metals - electropositive
• Non-metals - electronegative

DISCARDED: metalloids

Question 3

Dobereiner’s Triads

Answer 3

• Average of the masses of 1st and 3rd elements gives us the mass of the middle element .

a)Li Na K
7 23 39
b)Be Mg Ca
9 24 40
c) Ca Sr Ba
40 88 137

Question 4

Exception of Triads

Answer 4

1. Fluorine - 19
2. Chlorine - 35.5
3. Bromine - 80

Question 5

Newland’s Law of Octaves

Answer 5

When elements are arranged in increasing order of their atomic masses, the 8th element will have similar properties to the 1st element.

Drawback
1. Noble gases were not discovered
2. Was true only till Calcium - after which the gap is 18

Question 6

Lother Meyer’s Curve

Answer 6

• calculated atomic volume

Peak - ALKALI METALS
Trough - TRANSITION METALS
Increasing slope - HALOGENS
Decreasing slope - ALKALINE EARTH METALS

MERIT: Periodic properties are a function of the atomic masses

Question 7

Mendeleev’s Periodic Table

Answer 7

• 12 columns and 7 rows
• vacant spaces were left for elements that were not discovered
  Eka Silicon - Germanium
  Eka Aluminium - Gallium
  Eka Boron - Scandium
  Eka Manganese - Technitium
• correction of atomic weight
  Beryllium
  13.5/3 = 4.5 (equivalent weight)
  4.5*2 = 9 (Corrected Weight)

Question 8

What are orbitals and nodes?

Answer 8

1. Regions of high electron density
2. Regions with no chance of finding an electron

Question 9

What is periodicity and what is its cause?

Answer 9

1. The repetition of similar properties of elements are certain regular intervals is called periodicity
2. It is caused due to the repetition of similar EC after regular intervals

Question 10

What is periodicity and what is its cause?

Answer 10

1. The repetition of similar properties of elements are certain regular intervals is called periodicity
2. It is caused due to the repetition of similar EC after regular intervals

Question 11

Atomic Number 100

Answer 11

Fermium

Question 12

What is oxidation state?

Answer 12

It is the charge on an atom in its combined state.
- May/May not be the same as its valency

Na is more electro-positive than H –> NaH –> H^-1
O is more electro-negative than H –> H2O —> H^+1

Question 13

Zinc, Cadmium, and Mercury are different compared to other transition elements. Why?

Answer 13

1. Soft
2. Melting Point - low
3. Boiling Point - High

Question 14

Principal Quantum number

Answer 14

• denoted by ‘n’
• total number of electrons = 2n^2
• number of orbitals = n^2

Question 15

Azimuthal Quantum number

Answer 15

• associated due to the angular momentum of the electron
• denoted by l
  Values of l ==> 0 to (n-1)
  s subshell –> 0
  p subshell –> 1
  d subshell –> 2
  f subshell –> 3

Question 16

Magnetic Quantum Number

Answer 16

m ==> -l to zero to l

l = 0, m=0 —> No of orbitals = 1 (2e)
l = 1, m= -1,0,1 —> No of orbitals = 3 (6e)
l = 2, m= -2,-1,-0,1,2 —> No of orbitals =5 (10e)
l = 3, m=- 3,-2,-1,0,1,2,3 —> No of orbitals = 7 (14e)

Question 17

Aufbau Principle

Answer 17

(n+l) rule

     3s.     2s n       3.        2 l        0          0

—> electron enters the orbital with a low energy level
—> value of n is the tie-breaker

Question 18

What is the effective nuclear charge? (Zeff)

Answer 18

Zeff = Z - sigma (screening constant)
# Shielding effect: Innermost electrons repel the outer electrons which increases the atomic radius.
# Attraction on the outermost electron decreases.