Question

How Mosely proved that atomic number is more fundamental property of an element that its atomic weight ?

Answer 1

Mosely measured X-ray wavelength of elements and discovered that the wavelengths of X-rays was decreasing as the atomic number was increasing. This property was shown by elements except three pairs of elements. They were- argon and potassium, nickel and cobalt, tellurium and iodine.This showed that atomic number is more fundamental property of an element that its atomic weight.

Answer 2

Answer:

⇒(6.62 x 10⁻³⁴ x3x10⁸)/300x 10⁻⁹

=6.62 x 10⁻⁹J

so, Kinetic energy for for 1 mole of photons=6.62 x 10⁻⁹ x6.022 x 10²³

=3.99x 10⁵J

so ,minimum amount of energy required to remove 1 mole of electrons from sodium atoms is

=(3.99 x 10 ⁵)- (1.68 x 10⁵)

=2.31 x 10 ⁵J

∴  minimum energy required to remove 1 electron from Na atom=

⇒2.31 x 10⁵/6.022 x 10²³

⇒3.84 x 10⁻¹⁹ J

Now maximum wavelelngth = λ=hc/E=(6.62 x 10⁻³⁴ x 3 x 10⁸)/3.84x 10 ⁻¹⁹

=5.17 x 10⁻⁷m=517nm