Atomic Structure Flashcards
What is an isotope?
Atoms of the same element with the same number of protons but a different number of neutrons.
Why do isotopes have the same physical properties?
They have the same electron configuration as only neutron number differs, number of electrons determines physical properties.
What is relative atomic mass?
This is the mass of an atom relative to 1/12th the mass of an atom of Carbon-12.
Describe the first stage of time of flight spectroscopy. (Electro spray ionisation)
In electrospray ionisation the sample is dissolved in a volatile solvent and forced through a fine hollow needle that is connected to a positive terminal of a high voltage power supply. This produces a tiny positively charged droplets that have gained a proton from the solvent. The solvent evaporates from the droplets into the vacuum and the droplets get smaller until they contain no more than a single positively charged ion.
Describe the alternative first stage of time of flight mass spectroscopy (electron impact)
In electron impact, the sample is vaporised and high energy electrons are fired at it from an electron gun , which is a hot wire filament, with a current running through it that emits beams of high energy electrons. The usually knocks off one electron from each particle forming a 1+ ion .
Describe the acceleration stage of time of flight mass spectroscopy.
The positive ions are attracted towards a negatively charged plate and accelerate towards it. Lighter ions and more highly charged ions achieve a higher speed.
Describe the ion drift stage of time of flight mass spectroscopy
The ions pass through a hole in the negatively charged plate, forming a beam and travel along the a tube called the flight tube to a detector.
Describe the detection stage of time of flight mass spectroscopy.
When ions with the same charge arrive at the detector the lighter ones arrive first as they have higher velocities. The flight times are recorded. The positive ions pick up an electron from the detector which causes a current to flow. Current is proportional to the abundance of the isotope.
What is ionisation energy?
Ionisation energy is the energy required to remove a mole of electrons from a mole of an atoms in a gaseous state, to produce one mole of unipositive gaseous ions.
What is the general trend is ionisation energy across a period?
Increase as there is an increase in nuclear charge meaning there is a greater attraction between the outer electron and positive nucleus, making it increasingly difficult to remove an electron.
Why does the trend differ for the ionisation energy between magnesium and aluminium in period 3.
The ionisation energy should increase from Mg to Al should increase however, the ionisation of aluminium is lower than magnesium. This is because the outer electron in aluminium is being removed from the 3p orbital which is of a slightly higher energy than the 3s orbital, so less energy is required to remove from the 3p therefore aluminiums ionisation energy is lower.
What is the general trend down a group?
Decrease, this is because atomic radius increases down a group therefore the outer electron is further away from the nucleus due to more electron shells and therefore requires less energy to remove it.
