Physical - 1.1 Atomic Structure Flashcards
What happens in acceleration (TOF)?
The second stage of TOF spectrometry. The positively charged ions are accelerated by an electric field so that they have the same kinetic energy.
What is the atomic nucleus?
Positively charged object composed of protons and neutrons at the centre of every atom with electrons orbiting it.
Define atomic number
The number of protons in the nucleus.
What is electron impact ionisation?
Method of ionisation in TOF spectrometry. The sample is vapourised and an electron gun fires high energy electrons at it, causing an election to be knocked off each particle to produce 1+ ions.
What is electrospray ionisation?
Method of ionisation in TOF spectrometry. The sample is dissolved and pushed through a fine nozzle at a high pressure. A high voltage is applied to it causing each particle to gain an H+ ion. The sample is then turned into a gas.
Define first ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.
Define isotope
Atoms of the same element with the same number of protons but a different number of neutrons.
Define mass number
The total number of protons and neutrons in the nucleus.
Define second ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
What is a TOF spectrometer?
A method of mass spectrometry where an ions m/z ratio is determined by a time of flight measurement. Consists of four stages: ionisation, acceleration, in drift, and detection.
What is an electron configuration?
The distribution of electrons of an atom in orbitals.
What happens in ion detection?
Fourth stage of TOF spectrometry. The negatively charged plate detect charged particles and a mass spectrum is produced.
What happens in ion drift?
The third stage of TOF spectrometry. The ions enter region with no electric field so they drift through it. The light of the ion, the faster they will drift.
What happens in ionisation (TOF)
First stage of TOF. The sample can be ionised by electro spray ionisation or electron impact ionisation.
What did the plum pudding model represent?
It represented atoms as a sphere of positive charge, with small negative charges distributed evenly within it
What is the electron shell model (Rutherford)?
The atom consists of a small, dense central nucleus surrounded by orbiting electrons in electron shells
What is the relative charge and mass of a proton?
Relative charge = +1
Relative mass = 1
What is the relative charge and mass of a neutron?
Relative charge = 0
Relative mass = 1
What is the relative charge and mass of an electron?
Relative charge = -1
Relative mass = 1/1840
What is the mass number a sum of?
The sum of protons and neutrons in an atom
What is atomic number equal to?
The number of protons
What happens in ionisation (TOF)?
A sample of an element is vaporised and injected into the mass spectrometer where a high voltage is passed over the chamber. This causes electrons to be removed from the atoms leaving +1 charged ions in the chamber.
What happens in acceleration (TOF)?
These positively charged ions are then accelerated towards a negatively charged detection plate
What happens in acceleration (TOF)?
These positively charged ions are then accelerated towards a negatively charged detection plate
What happens in ion drift (TOF)?
The ions are deflected by magnetic field into curved path. The radius of their path is dependent on the charge and mass of the ion.
What happens in detection (TOF)?
When the positive ions hit the negatively charged detection plate, they gain an electron producing a flow of charge. The greater the abundance, the greater the current produced.
What happens in analysis (TOF)?
These current values are then used in combination with the flight times to produce a spectrum printout with the relative abundance of each isotope displayed
What is the equation for relative atomic mass using a spectra?
Ar = (m/z x abundance) / (total abundance)
How many electrons can be held in the S orbital?
Two
How many electrons can be held in the P orbital?
Six
How many electrons can be held in the D orbital?
10
What are the three rules for writing out electron configurations?
1) the lowest energy orbital is filled first
2) electrons with the same spin fill up and orbital first before pairing begins
3) no single orbital holds more than two electrons
Define ionisation energy
The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state
What is the trend in first ionisation energy along a period?
First ionisation energy increases due to decreasing atomic radius and greater electrostatic forces of attraction
What is the trend in first ionisation energy down a group?
First ionisation energy decreases due to an increasing atomic radius and shielding which reduces the effect of the electrostatic forces of attraction
Why is the first ionisation energy of aluminium lower than expected?
Due to a single pair of electrons with opposite spin. As a result, there is a natural repulsion which reduces the amount of energy needed to be put in to remove the outer electron.
