1.1 - Atomic Structure Flashcards
What is the mass of an electron?
1/2000
What is mass number?
Number of protons and neutrons in the nucleus
What is an isotope?
Atoms with the same number of protons but a different number of neutrons.
What did John Dalton describe atoms as?
Solid spheres. Different spheres make up different elements.
What did J.J. Thomson describe atoms as?
He discovered electrons and showed that atoms weren’t solid and indivisible. He formed the plum pudding model, with a positively charged “pudding” and negative electrons scattered on it.
Describe the gold foil experiment.
Ernest Rutherford and his students conducted this experiment. They fired positive alpha particles at a thin sheet of gold. The plum pudding model suggested that most alpha particles would be slightly deflected by the positive pudding. Instead, most of the particles passed straight through and small number were deflected backwards. Most of the atom is empty space.
What was Bohr’s model?
Electors exist in shell. When electrons move between shells, electromagnetic radiation is emitted or absorbed. This fitted experimental observations.
What was discovered after Bohr’s model?
Not all electrons in a shell have the same energy. Sub-shells were included, explaining bonding and ionisation energy trends.
What is relative atomic mass /Ar
Average mass of an atom of an element compared to 1/12 of a carbon-12 atom
What is relative isotopic mass? What’s special about it compared to Ar?
Mass of an atom of an isotope of an element compared to 1/12 of a carbon-12 atom. Ar is usually not a whole number, whereas relative atomic mass is usually a whole number.
What is relative molecular mass/ Mr
The average mass of a molecule compared to 1/12 of a carbon-12 atom.
What is electrospray ionisation?
Dissolve the sample and push through a small nozzle at a high pressure. Apply a high voltage to it. Each particle gains a H+ ion.
What is the equation for electrospray ionisation?
X (g) + H^+ -> XH^+ (g)
What is electron impact ionisation?
Sample is vaporised and an electron gun fires high energy electrons at it, knocking one electron off each particle to form 1+ ions
What happens in acceleration TOF?
Positively charged ions are accelerated by an electric field so they all have the same kinetic energy. Lighter ions move faster than heavier ions.
What happens in Ion drift TOF?
Ions enter a region with no electric field, so lighter ions drift faster than heavier ions.
What happens in detection TOF?
Lighter ions reach detector faster than heavier ions (in less time). Detector detects charged particles and forms an electric current when it is hit.
What does a mass spectrum tell you?
Y axis is abundance, x axis is m/z ratio. If the sample is an element, each line will represent a different isotope. The height of each peak would represent the relative isotopic abundance.
What would be the difference in a mass spectrum graph if electrospray ionisation is used?
H+ ion is added to each particle. Therefore each peak would be one unit greater than the relative mass of each isotope.
How do you calculate Ar from a mass spectrum?
(Abundance 1 x m/z 1) + (Abundance 2 x m/z 2)… / total abundance
What is the exception in electron configurations?
4s before 3d
Why are chromium and copper weird? What are their electron configurations?
They donate one of their 4s electrons to the 3d sub-shell. It is more stable with a full or half-full d sub-shell.
Cr (24e) - 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Cu (29e) - 1s2 2s2 2p6 3s2 3p6 4s1 3d10
What’s different about transition metals in terms of electron configuration?
When they become ions, they lose their 4s electrons before their 3d electrons.
From left to right on the period table, what are the blocks for the outer shell electrons?
S, d, p
