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
Describe ion drift
The ions enter a region with no electric field, so they just drift through it. Lighter ions will drift through faster than the heavier ones.
Step 4 of mass spec is _____
detection
Describe detection
because lighter ions travel at high speeds in the drift region, they reach the detector in less time than the heavier ones. The detector detects charged particles and a mass spectrum is produced.
A mass spectrum is _____/______ plotted against _________
mass/charge
abundance
Equation for calculating RAM when analysing spectra
RAM = m/z x abundance
____________________
total abundance
If the relative abundance is not given in percentage when calculating RAM you need to…
divide answer by 100
Elements with different _____ produce more than one line in a mass spectrum because the ______ have different masses.
isotopes
A molecular ion, M+, is formed in the mass spectrometer when one electron is removed from the molecule. This gives a peak in the spectrum with a mass/charge ratio equal to ________ ________ ____ of the molecule. This can be used to help identify the unknown compound.
relative molecular mass
Electron shells are made up of ___-______ and ________
sub-shells
orbitals
sub shell s p d
number
of 1 3 5
orbitals
Max 2 ? ?
electrons
6
10
- electrons fill up the ______ energy level first
- electrons fill orbitals ________ first before they start sharing.
- lowest
- singly
electron configuration of copper ?
1s2 2s2 2p6 3s2 3p6 4s2 3d9
electron configuration of chlorine using noble gas?
[Ne] 3s2 3p5
Define Pauli exclusion principle
Each orbital can hold a maximum of TWO electrons - must have opposite spins
Define Hunds rule
When filling the orbitals of a sub level, put one electron in each orbital before pairing them
Define Aufbau principle
lower energy levels fill before higher energy orbitals
Define first ionisation energy
energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Show the first ionisation energy of Na
Na(g) –> Na+(g) + e -
ionisation depends on 3 things
describe each
shielding
distance from nucleus
nuclear charge
more energy levels = less attraction
attraction decreases with distance
more protons in the nucleus = more positively charged the nucleus is = stronger the attraction for the electrons
A high ionisation energy means there’s a high ___________ between the electron and the nucleus and so more ______ is needed to remove the electron.
attraction
energy
Define second ionisation energy
the energy needed to remove 1 electron from each ion in 1 mole of gaseous +1 ions to form 1 mole of gaseous ions with a +2 charge
Show second ionisation energy of oxygen
O+(g) –> O2+(g) + e -
Why is there 2 dips in the graph showing period 3 elements first ionisation energy?
dips on 3rd element and 6th element
3rd = change from s to p
6th = electron has paired to p orbital so it repels
first ionisation energies of elements down a group ________
decrease
first ionisation energies of elements across a period generally _______
increase
Ionisation energy ________ down group 2
decreases
extra inner shells to shield and extra shell means that the outer electrons are further away meaning less attraction to the nucleus so less attraction
resulting in a lower ionisation energy
ionisation energy _______ across a period
increases
number of protons is increasing, which means a stronger nuclear attraction
