Quantum theory and electronic structure of atoms Flashcards
Losing and gaining electrons
The number of electrons is equal to the number of protons in an atom
atoms lose or gain electrons to form charged particles
Losing an electron will result in a positively charged atom
Gaining an electron will result in a negatively charged atom
Positively charged = cations
negatively charges = anions
cations and anions are always found together making their overall charge = 0
How electrons are arranged
Within shells: size and energy of shell
Within subshells: Shape of orbitals
Within orbitals: orientation of orbitals in space
Spin quantum number: indicates the spin of the electron
Max Planck analysed data on radiation emitted by hot solids
when solids are heated they emit EM radiation over a range of wavelengths
discovered that atoms and molecules emit energy only in certain discrete quantities
Planck’s quantum theory
atoms and molecules can emit or absorb any amount of energy
can emit or absorb only in discrete and definite quantities-small packages or bundles
Planck gave the name quantum to the smallest quantity of energy that can be emitted or absorbed in the form of electromagnetic radiation
The energy of a quantum
E = hv (E = energy, v = frequency of the radiation)
energy is only emitted in integral quantities 1hv, 2hv, 3hv etc (not 1.75hv)
Photoelectric effect (demonstrates that light has particles like qualities)
the emission of electrons from certain metals when they are exposed to light from a certain minimum frequency (energy)
electromagnetic radiation
energy that is propagated through free space or through a material medium in the form of electromagnetic waves, such as radio waves, visible light and gamma rays
light carries energy in the form of tiny particles known as photons. The amount of energy that the light has depends on its wavelength
formula for calculating the energy of a photon
E = hf
E = energy
h = planck’s constant
f = frequency of the radiation
f = c/λ
E = hc/λ
The higher the frequency the higher the energy of the photon
frequency
the number of waves per second that pass a particular point in space
short wavelength = high frequency
continuous spectrum vs line spectrum
When white light is passed through a prism it gives a continuous spectrum
When white light is passed through a gas or electricity is passed through it, it gives a line spectrum
when electrons are on different energy levels
They represent different colours of light
When an electron moves up an energy level it absorbs energy
When an electron movs down an energy level it releases energy in the form of light (Photon)
Bohr’s conclusions
each electron lies at a definite radius from the nucleus and has a fixed energy
An electron can jump from one energy level to another by absorbing a fixed amount of energy
That electron can also move down energy levels by releasing that same amount of energy
An emission spectrum arises when electrons that have been excited up an energy level, then drop down an energy level emitting that energy as light of a given frequency
limitations of Bohr model
Only accounts for hydrogen atom
Accounts as electrons only having particle like properties and not wave-like properties
restricted to orbiting the nucleus at fixed distances
Heinsenburg’s uncertainty principle
You can only predict the position of an electron within an atom or its speed but not both at the same time
Orbitals
a cloud of electron density around the nucleus which represents a probability of where an electron is likely to be at any time
