Atomic structure Flashcards
What is the relative mass of an electron?
1/2000
What is the definition of an ion?
Atoms with the same number of protons and neutrons, but have lost or gained electrons
What is the definition of an isotope?
Atoms with the same number of protons, but a different number of neutrons
What was Dalton’s theory on the structure of the atom?
Solid spheres that make up different elements
What is the plum pudding model and who suggested this theory?
-Positively charged sphere with negatively charged electrons scattered throughout it
-JJ. Thompsons theory
What experiment did Rutherford carry out and what were his conclusions?
-Gold foil experiment
-Fired alpha particles at gold foil, some were deflected back instead of passing straight through
-Conclusions –> positive nucleus in the centre, cloud of negative electrons, mostly empty space
What were the principles of Bohr’s model of the atom?
-Electrons only exist in fixed orbitals
-Each shell has a fixed energy
-When an electron moves between shells electromagnetic radiation is emitted or absorbed
-Radiation will have a fixed frequency
Define relative atomic mass.
The average mass of an atom of an element relative to 1/12 of the mass of an atom of carbon-12
Name the four stages that occur during mass spectrometry.
-Ionisation (electrospray ionisation or electron impact ionisation)
-Acceleration
-Ion Drift
-Detection
What is electrospray ionisation?
-A sample is dissolved in a solvent and pushed through a small nozzle at high pressure
-High voltage applied, so each particle gains a h+ ion
-Solvent is removed, leaving a gas of positive ions
What is electron impact ionisation?
-Sample is vapourised and an electron gun is used to fire energy electrons at it
-Knocks one electron off each particle so they become 1+ ions
What happens during acceleration in mass spectrometry?
-Positive ions accelerated by an electric field
-Each ion gains the same kinetic energy
-Lighter ions=greater acceleration
What happens during ion drift in mass spectrometry?
-Ions enter region with no electric field
-Drift through at same speed they entered
-Lighter ions=drift at higher speeds
What happens during detection in mass spectrometry?
-Lighter ions reach detector first
-Detects the current created when ions hit the detector and record how long it took them to pass through the spectrometer
-Data collected used to calculate mass/charge values
How do you calculate relative atomic mass using a mass spectrum?
-Multiply the mass/charge and % abundance for each isotope
-Add them all together
-Divide by 100
What is the definition of ionisation energy?
Energy required to remove an electron from each atom in one mole of gaseous atoms to form one mole of charged ions
What are the three factors that affect ionisation energy?
-Nuclear charge–>more protons=stronger attraction to electrons
-Distance from nucleus–>closer to nucleus=more attraction
-Shielding–>more shells=less attraction
What is the ionisation trend in group 2?
The first ionisation decreases as you go down group 2
What is the trend in ionisation as you go across a period?
-Generally the ionisation energy increases as you go across a period due to an increase in protons
-Slight drop between groups 2 and 3 and groups 5 and 6
Why does the ionisation energy drop between groups 2 and 3?
-Group 3 elements have an outer electron in a p orbital which has a higher energy than an s orbital so electron is found further from the nucleus
-p orbitals also have more shielding
Why does the ionisation energy drop between groups 5 and 6?
In group 6 elements, the outer electron is in an orbital with two electrons, which repel each other so electrons are easier to remove
