Topic 2: Atomic Structure

• all matter is made up of tiny particles called atoms • an element consists of atoms of a single type • compounds are a combination of 2 or more types of atoms • atoms can’t be created/destroyed in a chemical reaction, only rearranged

an isotope of a chemical element that has an unstable nucleus, which emits certain radiations.

• radiocarbon dating: C-14 exists in a set ratio to C-12 in living organisms, and when it dies, the C-14 isotopes decay, altering the ratio • radiotherapy: Co-60 is a powerful gamma emitter used to treat cancer • medical tracer: I-131 releases gamma and beta radiation and can be used to detect if the thyroid is functioning correctly + treat thyroid cancer

• vaporisation • ionisation • acceleration • deflection • detection

• high vacuum so particles don’t collide with air - all particles are converted to gaseous state

• gaseous atoms are bombarded with high-energy electrons • to generate positively-charged species e. g. X (g) + e- -> M+ (g) + 2e-

• the ions are attracted to positively-charged plates • accelerated in the electric field • so they all have the same KE

• the positive ions are deflected by an electromagnetic field • degree of deflection depends on mass-to-charge ratio • high deflection: low mass, high charge

high charge to low mass ratio

• the beam of ions passing through the detector plate is electrically detected • species of a particular m:z ratio are identified • results are called “mass spectrum”

a spectrum of wavelengths comprised of the types of electromagnetic radiation

• has electric and magnetic fields that oscillate perpendicularly to each other and to the direction of travel • behaves like both a particle and like a wave • velocity of EM waves = velocity of light • can travel in a vacuum

highest wavelength, lowest frequency

lowest wavelength, highest frequency

as wavelength increases: • quanta energy decreases • frequency decreases

• pass electromagnetic radiation (e.g. light) through a collection of cold gas • atoms will absorb some radiation at a certain frequency • the spectrometer will compare the transmitted radiation to initial radiation and produce the absorption spectrum

• continuous spectrum of colours • with vertical black lines at seemingly random intervals • lines indicate absence of transmitted radiation

• heat gas with electric sparks 2. observe the output through a spectrometer

a black background with seemingly random vertical lines of colour (follows colour spectrum placements)

• electrons move in orbit around protons • the forces of attraction are balanced by the acceleration of electrons at high velocity • the closer the electron to the nucleus, the more stable the electron • if energy was negligible, electrons could travel to any shell

• electrons absorb energy in the form of photons • they get excited to a higher energy level if the photon’s energy >= energy difference between initial and final energy levels • due to decreased stability in higher energy levels, electrons emit energy to go back to ground state

elements/ions that have the same electronic config.

it isn’t possible to measure the position AND velocity of a microscopic particle with 100% certainty.

it’s impossible to locate a microscopic body without disturbing its position/velocity