Identifying elements

Question 1

What is emission spectroscopy

Answer 1

• all elements have specific energy levels
• electrons exist in the lowest possible energy level
• when energy is supplied, it’s absorbed by the electrons and they jump to a higher level (excited state)
• but this is unstable so it quickly drops back to a lower energy level
• when it does this, it releases energy in the form of light of a specific frequency
• then a spectroscope is used to separate frequencies to form an emission spectral lines
• can be used to identify elements

Question 2

What is the flame test?

Answer 2

• all elements have specific energy levels
• electrons exist in the lowest possible energy level
• when they’re heated, the energy is absorbed by the electrons and they jump to a higher level (excited state)
• but this is unstable so it quickly drops back to a lower energy level
• when it drops, it emits a specific coloured flame, with a specific wavelength of light
• the colour can be used to identify the element

Question 3

Atomic absorption spectroscopy:

Answer 3

• it uses light absorption to measure the amount of an element present in a sample
  Steps:
  1. Element is analysed using a qualitative method
• helps to focus on just one element
  2. Light of the correct wavelength is generated
• using a hollow cathode lamp made of the element being detected so that it generates the correct wavelength
  3. Sample is vaporised
• done by spraying liquid form into an energy source turning it into individual atoms
  4. The light passes through the sample
• only the element being tested will absorb it
• greater concentration = more light absorbed
  5. Light that passes through is focused through a slit and enters a monochromator
• separates absorbed wavelengths from others
  6. The specific selected wavelength goes through a detector
• measures intensity of light
• a calibration curve can be used to determine concentration
  higher amount of the element = more absorbed

Question 4

Absorbance value

Answer 4

measure of how much light passed without being absorbed