Question

Please answer these 3 questions a) b) and c), i will mark you Brainliest

Answer 1

(a) Doberiner's triad

adv: the average of atomic masses of 2 elements in a triad will be equal to the atomic mass of middle element

      eg:   Li,Na,K

              atm of Li: 6.9

              atm of Na: 23

              atm of K: 39

  ∴          $\frac{6.9+23}{2}$

              $\frac{45.9}{2}$

              $\frac{46}{2}$    (rounding to 46)

              23 = atm of Na

lim: he could only explain 3 traids and it was not applicable for other elements

Newland's octave rule

adv: he found that chemical features of elements are being repeated after every  $8^{th}$ element

lim: he could only explain it upto Ca and other smaller elements

Mendeleev's periodic table

adv: it explained about features related to atomic masses and reactivity towards hydrogen and oxygen of an element

lim: he could not place hydrogen as it reacted equally with left and right side elements and couldn't place isotopes

(b) Henry Moseley

(c) Modern periodic law states that

              " Properties of elements are periodic functions of its                                atomic numbers "

hope so its helpful :)