Hydrogen Atom Spectrum

Question 1

What happens when an atom is heated? x2

Answer 1

When an atom is heated, it absorbs energy as it becomes excited, which is re-emitted as radiation as it falls down to its ground state.

Question 2

Characteristic of this radiation when seen using a prism?

Answer 2

Series of discrete lines Each discrete line = different energy = different wavelength = different frequency

Question 3

How does the frequency / energy differ when a given atom absorbs and emits radiation?

Answer 3

The EM radiation absorbed and emitted have the same frequency for a given atom.

Question 4

Main difference between emission spectra and absorption spectra?

Answer 4

Emission = colours Absorption = gaps

Question 5

Difference between wavelength and frequency?

Answer 5

Literally what it means.

Wavelength = length of wave (short or long)

Frequency = how many waves in a given time

Question 6

Relationship between wavelength and frequency?

Answer 6

Shorter (smaller) wavelenth = higher frequency (high energy)

Longer (larger) wavelength = lower frequency (low energy)

Question 7

What is the emission spectrum?

Answer 7

The amount of light emitted at different wavelengths is called an emission spectrum.

Only specific wavelengths i.e. colours are seen.

Question 8

What is the unit of measurement for wavenumber?

Answer 8

cm^-1

Question 9

What is the unit of measurement for wavenumber?

Answer 9

nm

Question 10

What is the symbol to represent wavelength?

Answer 10

λ

units = nm

Question 11

How to figure out wavenumber (cm^-1) from wavelength (nm)?

Answer 11

wavenumber = 1 / λ

i.e. reciprocal of wavelength = 1 over wavelength

Question 12

What is the formula to predict the energies of the observed lines in an emission spectra?

Answer 12

wavenumber = 1/λ = R_H (1/m² - 1/n²)

Question 13

What is the Rydberg constant and what is it used for?

Answer 13

R or R_H = 1.097 x 10⁵ cm^-1

Question 14

What does m stand for in the wavenumber formula?

Answer 14

m = innermost shell

Question 15

What does n stand for in the wavenumber formula?

Answer 15

n = bigger integer than m

Question 16

What are the three IR series called?

Answer 16

m = 3 = Paschen series (IR)

m = 4 = Brackett series (IR)

m = 5 = Pfund series (IR)

Question 17

What are the frist two series called?

Answer 17

Lyman (UV) & Balmer (partly visible)

Question 18

Which series has more energy?

Answer 18

Lyman > Balmer > IR (Paschen, Brackett, Pfund)

Question 19

Why does Lyman series have higher energy than IR series?

Answer 19

Shorter wavelength and higher frequency.

Question 20

Which series has longer wavelength, Lyman or Paschen?

Answer 20

Paschen series has longer wavelengths.

Question 21

What does n stand for?

Answer 21

n = principle quantum no.

n = main energy level

n = shell

Question 22

Why does higher principle quantum no. (n) have higher energy levels?

Answer 22

This is because the shells become more far away from the nucleus as the principle quantum number increases.