Question

What is the frequency, in s−1, of the light emitted when the electron in a hydrogen atom drops from the energy level ni = 12 to nf = 5?

Calculate the de Broglie wavelength, in nanometers, associated with a 145 g baseball traveling at a speed of 179 km/h?

How many orbitals have the values n = 4, l = 3, and ml = -2?

Without referring to any tables or listings in the text, name the elements provided for each of the following.

A sixth-period element whose atoms have three unpaired p electrons?

A d-block element having one 4s electron?

A p-block element that is a metal?

Answer 1

From Rydburg's Equation , 1/ λ = R[(1/n_i²) – (1/n_f²)]
   Where R = Rydburg's constant = 10.96 x10⁶ m^-1
               λ = wavelength = ?
               n_i = 5
               n_f = 12
Plug the values we get 1/λ = 362.29x10³  

Frequency,v = c/λ = cx(1/λ)

Where c = speed of light = 3.0x10⁸ m/s

So v = 3.0x10⁸ x362.29x10³ = 1.087x10¹⁴ s^-1

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According to de Broglie wave length, λ = h/mv
Where

h = plank's constant = 6.625x 10^-34 Js

λ = wave length = ?

m = mass of object = 145 g

v = velocity of object = 179 km/h = 179x0.278 m/s = 49.762 m/s

Plug the values we get λ = 9.18x10^-38 m

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There is only one orbital with n = 4, l = 3, and ml = -2

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A sixth-period element whose atoms have three unpaired p electrons?

three unpaired p electrons menas it belongs to VA group & it is the 6th period element .So the element is Tl.

A d-block element having one 4s electron?

It is Potassium (K)

A p-block element that is a metal is Gallium