Atomic structure and periodic table Flashcards
equation to calculate maximum number of electrons in a shell?
max electrons in shell = 2n^2
What is mass number and what is its symbol?
symbol = A
The sum of protons and neutrons in an atom
What is atomic number (proton number) and what is its symbol?
symbol = Z
Equal to the number of protons in an atom
What is an isotope?
Atoms of the same element with the same atomic number, but with different number of neutrons , resulting in different mass number.
What is relative atomic mass (Ar)
The mean mass of an atom of an element, relative to one twelfth of the mean mass of an atom of the carbon-12 isotope.
What is isotopic mass?
The isotopic mass of an isotope relative to one twelfth of the mean mass of an atom of the carbon-12 isotope
What is relative molecular mass?
The mean mass of a compound, relative to one twelfth of the mean mass of an atom of the carbon-12 isotope.
What happens in a time of flight spectrometry (TOF)?
Records time it takes for ions of each isotope to reach a detector.
Describe first stage of TOF
Ionisation - A sample of an element is vapourised and injected into the mass spectrometer where a high voltage is passed over the chamber. This causes electrons to be removed from atoms leaving +1 charged ions in the chamber.
Describe second stage of TOF?
Acceleration - These positively charged ions are then accelerated towards a negatively charged detection plate.
Describe third stage of TOF?
Iron drift - The ions are deflected by a magnetic field into a curved path. The radius of their path is dependent on the charge and the mass on the ion.
Describe Fourth stage of TOF?
Detection - When the positive ions hit the negatively charged detection plate they gain an electron producing a flow of charge. The greater abundance the greater the flow of charge.
Describe fifth stage of TOF?
Analysis - These current values are then used in combination with flight times to produce a spectra print-out with the relative abundance of each isotope displayed.
What happens if a 2+ ion is produced in TOF?
Will be more affected by magnetic field producing a curved path of a smaller radius. So, mass to charge ratio (m/z) is halved
Equation for Ar using TOF data?
Ar = (m/z*abundance)/ total abundance
What does the tallest peak correspond to in TOF on a molecule and what is this peak known as?
relative atomic mass and know as the molecular ion peak
What is ionisation energy?
The minimum energy required to remove one mole of electrons from one mole of atoms in a gaseous state. Measured in KJ
Why does the required energy increase for successive ionisation energies?
Electrostatic force between positive nucleus and outer shell electrons increases. Therefore more energy required to overcome this attraction.
What is the trend of first ionisation energies across a period and why?
The first ionisation energy increases due to a decreasing atomic radius and increase in proton number so increased electrostatic attraction.
What is the trend of first ionisation energies down a group and why?
First ionisation energy decreases due to an increase in atomic radius and an increase in electron shielding which reduces the effect of electrostatic attraction
What does it mean if there is a large increase when plotting successive ionisation energies on a graph and why?
Indicates a change in energy level because the electron is being removed from an orbital closer to the nucleus.
What provides the evidence for the existence of quantum shells?
emission spectra
What do successive ionisation energies provide evidence for?
Quantum shells and suggests and which group an element belongs to.
What provides evidence for the existence for electron subshells?
The first ionisation energy of successive elements.
