Unit 1 Inorganic Chemistry: Key Area 1 - Electromagnetic Radiation and Atomic Spectra Flashcards
What is the wavelength of a wave?
The distance between two crests of a wave. (measured in nanometers/ 10^-9)
Define the frequency of a wave.
The number of wavelengths that pass a certain point in one second. (measured in Hertz/Hz
What is the speed of electromagnetic radiation?
3x10^8 m/s
What does the symbol L stand for?
Avogadro’s constant
What does the symbol ‘c’ stand for?
Velocity
What does the symbol ‘h’ stand for?
Planck’s constant
When electromagnetic radiation acts more like particles than waves what are these called?
Photons
What is the formula to calculate the energy carried by a photon?
E=hf
How do you convert J mol^-1 to kJ mol^-1?
Divide by 1000
What is the atomic emission spectrum?
A coloured light obtained by passing high voltage electricity through a gas tube at low pressure. You can analyse this light by passing it through a prism. This light is diffracted and a series of lines is shown. These lines are the atomic emission spectrum of an atom/ molecule
What causes atomic emission spectra?
When an excited electron loses energy and jumps back down to either its ground state or a lower energy level and the lost energy is released in the form of photons. Each line corresponds to the energy given out when an excited electron moves to a lower energy state.
What causes atomic absorption spectra?
When the electrons are promoted and absorption spectrum is produced by measuring what wavelengths have been absorbed by the sample. This is also specific to a particular element.
What is the visible region of the spectrum?
400-700nm
What is the ultra violet range?
200-400nm
What happens when atoms absorb photons?
Electrons in the atom gain energy and are now in an excited state
What happens when atoms emit photons?
They lose energy and return to the ground state
What are 6 forms of electromagnetic radiation?
- Gamma rays
- X rays
- UV radiation
- Visible light
- Infrared radiation
- Radio waves
What is the frequency and energy of a short wavelength?
High frequency and high energy
What is the frequency and energy of a long wavelength?
Low frequency and low energy
In what ways can electromagnetic radiation be described?
Electromagnetic radiation can be described as a wave (has a wavelength and frequency), and as a particle, and is said to have a dual nature
When photons are emitted or absorbed, what happens to the energy?
When a photon is absorbed or emitted, energy is gained or lost by electrons within the substance
What is the relationship between the transfer of energy and frequency?
The photons in high frequency radiation can transfer greater amounts of energy that the photons in low frequency radiation.
What do photons carry?
A photon carries quantised energy proportional to the frequency of radiation
What happens when energy is transferred to atoms?
When energy is transferred to atoms, electrons within the atoms may be promoted to higher energy levels
When does an atom emit a photon of light energy?
An atom emits a photon of light energy when an excited electron moves from a higher energy level to a lower energy level
Why are lines produced in an emission spectrum?
- Energy is absorbed resulting in electrons being promoted to a higher energy level
- Lines produced from electrons falling to ground state emit energy corresponding to the wavelength of one of the lines.
