Hydrogen Spectrum+ionisation Energy

Question 1

Why are there more than one line?

Answer 1

Excited electrons drop back to different energy levels

Question 2

Explain how the lines in the atomic emission spectrum are formed. (4 marks)

Answer 2

1. Electrons are excited and jump to higher energy levels
2. Energy is quantised
3. Electrons drop from high energy levels to low energy level
4. Energy is emitted as light

Question 3

Explain how to calculate ionisation energy from the emission spectrum?
Hence, molar first ionisation energy?

Answer 3

1. Find convergence limit in
2. Lyman series
3. Use E=hf
   (4. Multiply by Avogadro constant)

Question 4

Explain why hydrogen atoms emit only certain definite frequencies of visible light. (2 marks)

Answer 4

1. Electrons fall from higher energy levels to n=2

2. Difference between any two energy levels is fixed

Question 5

Explain what does ionisation energy mean. (2 marks)

Answer 5

1. Energy required to remove an electron from hydrogen(for an electron to go from n=1 to n=♾
2. In gaseous state

Question 6

In 1st ionisation energy against atomic number graph, where the drops and why?

Answer 6

8-1 : only one electron in the outermost shell
2-3 : only one in the p-orbitals
5-6 : paired electrons repulsion

Question 7

Give electronic configuration of a nitrogen atom. And use this to explain how electrons are arranged in atoms. (7 marks)

Answer 7

1. Electronic configuration
2. Electrons within atoms occupy fixed energy levels or shells of increasing energy / nitrogen has electrons in two shells
3. Electrons occupy atomic orbitals within these shells /The first shell in nitrogen has s orbitals and the second shell s and p orbitals (1)
4. A maximum of two electrons can occupy any orbital / Each s orbital in nitrogen contains two electrons (1)
5. Each with opposite spins (1)
6. Orbitals of the same type are grouped together as a sub-shell / There are three p orbitals in nitrogen’s p sub-shell (1)
7. Each orbital in a sub-shell will fill with one electron before pairing starts / In nitrogen’s p sub-shell each orbital contains one electron (1)

Question 8

State how the first 3 ionisation energies of calcium would differ from those of potassium. (2marks)

Answer 8

1. 1st and 3rd will be higher

2. 2nd will be smaller

Question 9

How an atomic absorption spectrum is formed? (2 marks)

Answer 9

electrons move from lower energy levels to higher energy levels (1)
by absorbing specific frequencies of light (1)

Question 10

What are the similarities and differences between hydrogen 1, hydrogen 2 and hydrogen 3?

Answer 10

Same:
Same no of protons and electrons
Different:
0,1,2 neutrons

Question 11

Can ionisation energy be calculated using Balmer series? (2marks)

Answer 11

1. Balmer series corresponds to energy transitions involving n = 2 (1)
2. for ionisation energy need Lyman series / energy transitions involving n = 1 (1)

Question 12

Explain why 2nd IE is higher than 1st IE?

Answer 12

Electron being removed from a positive ions

Question 13

Balmer series points

Answer 13

1. n=2
2. Visible light
3. Line converges at higher freq

Question 14

Suggest why no more that first ionisation energy is used to ionise atoms in mass spectrometer

Answer 14

So no more than / only 1 electron is knocked out