Atomic Structure Flashcards
Define isotope
isotopes are atoms of the same element with different numbers of neutrons
What decides the chemical properties of an element? And how does this effect isotopes
number and arrangement of electrons decides the chemical properties
isotopes have the same configuration of electrons so they have the same chemical properties
Why do isotopes of an element have slightly different physical properties?
physical properties tend to depend on the mass of the atom
19th century: What did John Dalton say atoms were?
Solid spheres
Different spheres made different elements
(All atoms of an element = same mass)
1897: What did J.J. Thomson discover and what did it show?
Discovered the electron
Showed atoms weren’t solid
(Model known as ‘plum pudding model’)
1909 - Ernest Rutherford: What did he find out?
Conducted the golden foil experiment:
Fired positively charged alpha particles at a very thin sheet of gold
Particles passed straight through gold & only small no. of particles were deflected backwards (pulm pudding model said = alpha particles would be deflected by the positive ‘pudding’ in atom)
= developed into nuclear model of atom
Tiny positive nucleus surrounded by ‘cloud’ of negative electrons - most of atom is empty space
What was Niels Bohr’s model & discovery?
Model: where electrons exist in shells or orbits of fixed energy
Discovered: When electrons move between shells, electromagnetic radiation (with fixed energy or frequency) is emitted/absorbed
What have modern day scientists discovered & so what did they do?
Electrons in same shell ≠ same energy
Bohr model = wrong ∴ they refined it & added sub-shells
(Isn’t perfect model but it’s simple and explains many experimental observations e.g. bonding & ionisation energy trends)
Define relative atomic mass
the average mass of an atom compared to 1/12 mass of an atom of C12
Define relative molecular mass
the average mass of a molecule compared to 1/12 mass of an atom of C12
Relative masses can be measured by using a ____ ____________
mass spectrometer
Step 1 is ______ and the 2 ways of doing this
ionisation
electrospray ionisation
electron impact ionisation
Describe electrospray ionisation
The sample is dissolved and pushed through a small nozzle at high pressure. A high voltage is applied to it, causing each particle to gain a H+ ion. The sample is turned into a gas made up of positive ions.
Describe electron impact ionisation
The sample is vaporised and an ‘electron gun’ is used to fire high energy electrons at it. This knocks one electron off each particles so they become +1 ions.
Step 2 of mass spec is _____
Acceleration
Describe acceleration
The positively charged ions are accelerated by an electric field so that they all have the same kinetic energy. ( This means that the lighter ions will move faster than the heavier ones)
Step 3 of mass spec is _____
ion drift