Topic 1 Atomic Structure And Periodic Table Flashcards
State proton symbol, relative mass, relative charge and position:
p, 1, +1, nucleus
State neutron symbol, relative mass, relative charge, position
n, 1, 0, nucleus
State electron symbol, relative mass, relative charge, position
e-, 1/1840, -1, energy levels
What is relative isotopic mass?
The mass of the isotope on a scale on which a carbon-12 atom has a mass of exactly 12 units.
What is Relative atomic mass?
The Ar of an element is the mass of one of its atoms relative to 1/12th the mass of one atom of carbon-12
Why is the relative atomic mass of an element frequently not a whole number?
The Ar of an element is the average mass of the isotopes taking into account each isotopes abundance.
What is mass spectrometry?
It’s an accurate instrumental technique used to determine the relative isotopic mass and the relative abundance of each isotope.
What is the Molecular ion peak (M peak)?
The peak with the highest mass-to-charge ratio.
How does Time of Flight (TOF) Mass Spectrometry work?
It records the time it takes for ions of each isotope to reach a detector. Using this, spectra can be produced showing each isotope present.
Describe the first step of TOF Mass Spectrometry?
Ionisation - A sample of an element is vaporised and injected into the mass spectrometer where a high voltage is passed over the chamber. Causing electrons to be removed from the atom (they are ionised) leaving +1 charged ions in the chamber.
Describe the second step of TOF Mass Spectrometry?
Acceleration - These positively charged ions are then accelerated towards a negatively charged plate.
Describe the third step of TOF Mass Spectrometry
Ion drift - The ions are then deflected by a magnetic field into a curved path. The radius of their path is dependent on the charge and mass of the ion.
Describe the fourth step of TOF Mass Spectrometry?
Detection - When the positive ions hit the negatively charged detection play, they gain an electron producing a flow of charge. The greater the abundance, the greater the current produced.
Describe the fifth step of TOF Mass Spectrometry?
Analysis - These current values are then used in combination with the flight times to produce a spectra print-out with the relative abundance of each isotope displayed.
What happens if during the ionisation process a 2+ ion is produced?
It will be affected by the magnetic field producing a curved path of a smaller radius. As a result, it’s mass to charge ratio is halved and this is shown on the spectra as a trace at half the expected m/z value.
Who developed the ‘Quantum theory’ and what does it state?
Planck developed it and it states that energy exists in fixed amounts called quanta.
What did Bohr propose with use of the ‘Quantum theory’?
Bohr applied Planck’s theory to electrons. He proposed that electrons could only exist in fixed energy levels (quantum shells).
What is the evidence for the current electronic configuration?
- Emission spectra provide evidence for the existence of quantum shells
- Successive ionisation energies provide evidence for quantum shells within atoms and suggest the group to which the element belongs to
- The first ionisation energy of successive elements provides evidence for electron sub shells
What are orbitals?
Clouds of negative charge where electrons are held
Names of the different types of orbitals and their shapes
S, P, D and F. S-orbitals are spherical. P-orbitals are dumb-bell shaped. D-orbitals come in various shapes.
Each element corresponds to blocks within the periodic table. Why?
S-Block is group 1 and 2. D-Block is the transition metals. P-Block is groups 3-0. F-Block are elements that don’t fit in the table. Each element in their block has outer electrons in their respective orbital.
What is spin?
Within an orbital, electrons pair up with opposite spin so that the atom is as stable as possible. Electrons in the same orbital must have opposite spins.
State the 3 rules for writing the electronic configuration?
- The lowest energy orbital is filled first
- Electrons with the same spin fill up an orbital first before pairing begins
- No single orbital holds more than 2 electrons
Exceptions for rules of electronic configuration:
If electron spins are unpaired and therefore unbalanced, it produces a natural repulsion between the electrons making the atom very unstable. If this is the case, the electrons may take on a different arrangement to improve stability.
What is Pauli’s exclusion principle?
Two electrons can go in each orbital, providing they are of opposite spin
Hund’s rule of maximum multiplicity
Placing two electrons in one orbital means that, as they are both negatively charged, there will be some electrostatic repulsion between them. Placing each electron in a separate orbital reduces the repulsion and the system is more stable.
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 kjmol-1
Pattern of effective nuclear charge on the periodic table
Across the period, it increases
How to measure atomic radii
Dividing the distance between the two nuclei by two
Which radius can be determined in noble gases?
Van der Waal’s since they exist as atoms which do not bond with other elements
Why does the atomic radii decrease across a period?
- Number of protons in nucleus increases, therefore nuclear charge increases. Meaning attractive force between the nucleus and outer electrons increases.
Atomic radius decreases and increases…
Atomic radius increases down the group and decreases across the period
Electronegativity increases and decreases…
Electronegativity increases across the period and decreases down the group
