3.5 Energy levels and spectra

Question 1

Explain why the line spectrum of an element is unique to that element and can be used to identify it?

Answer 1

» Energy levels of those atoms are unique to that atom
» Photons emitted have energy equal to the difference in the levels
» Therefore photon energies are characteristics of the atom

Question 2

Why does no other element produce the same pattern of light wavelengths?

Answer 2

» Because the energy levels of each type of atom are unique to the atom

Question 3

What is a continuous spectra?

Answer 3

» All wavelengths of photon are emitted
» Such as a light bulb

Question 4

What is absorption spectra?

Answer 4

» Certain wavelengths of light are used by electrons to jump from one energy level to another
» E.g corona of sub blocks certain colors

Question 5

What is emission spectra?

Answer 5

» Certain wavelengths of light are emitted when electrons de-excite

Question 6

What is each line in a line spectrum due to?

Answer 6

» Light of a certain color and therefore a certain wavelength

Question 7

What do the photons have in common that produce the same line?

Answer 7

» Have the same energy

Question 8

When is each photon emitted in a line spectrum?

Answer 8

» When one of its electron de-excites

Question 9

What is the energy of the emitted photon equal to?

Answer 9

» hf = E1 - E2

Question 10

What are 2 differences between the line spectrum and the continuous spectrum?

Answer 10

» Line spectrum consists of discrete colored lines, whereas the continuous spectrum has a large spread of colors
» Line spectrum is due to photons of certain energies, whereas a continuous spectrum is due to a continuous spread of photon energies

Question 11

Explain how changes of electron energies can produce a line emission spectrum?

Answer 11

» Excitation is needed to produce an emission spectrum
» Electrons can only exist at discrete energy levels
» An electron falls from one level to another
» Which cause photon emmision, which has a definite wavelength

Question 12

What happens in an atom when line spectra are produced?

Answer 12

» Electrons move from one energy level to another
» Emitting or absorbing a definite wavelength

Question 13

Explain, why the emitted electrons have a range of kinetic energies up to a maximum value?

Answer 13

» Each photon has a certain/definite amount of energy
» Each electron absorbs the photon - Idea of 1:1 interaction
» Ek(max) = hf - work function, there is a maximum value
» Deeper electrons in the surface of the metal have to overcome more resistance to reach the surface as they lose kinetic energy colliding with other electrons

Question 14

What must happen in order for an existing scientific theory to be modified?

Answer 14

» An experiment must be performed to check the validity of the theory
» If the experiment doesn’t agree with the theory, theory has to be changed
» If experiment agrees, peer review and more experiments are needed for the theory to be modified