Unit 1- Atomic and electronic structure Flashcards
Define atomic numbers
Number of protons in an atom or ion
Define mass number
Number of protons and neutrons in the nucleus
Define isotopes
atoms of the same elements with the same atomic number but different mass number therefore same proton but different neutrons
Define first ionisation energy
Amount of energy per mole to remove an electron from each gaseous atom to form a singly positive ion
Define second ionisation energy
Energy change per mole for the removal of an electron from a singly positive ion to a doubly positive ion
Define 1st electron affinity
Energy change per mole to add an electron to a gaseous atom to form a negative ion
Define 2nd electron affinity
Energy change per mole to add an electron to a negative ion to a double negative ion
Define orbitals
The region where an electron is most likely to be found within a shell
Explain mass spectrometry
- Sample must be in a gaseous state
- Sample is injected into the machine and is vaporised
- Vapour is bombarded with high energy electrons therefore forming positive ions
- Ions are accelerated by an electric field
- Ions enter a magnetic field which deflects the ions
- Detector detects the ion
What affects how much an ion is deflected?
- Mass of the ion- Heavier ions deflected less
- Charge of the ion- Smaller charge deflects less
What does a mass spectrum show?
- Height of the peaks show abundance
- The peaks show the differnent isotopes present
- relative atomic mass = sum of (mass of each isotope x percentage of that isotope)/100
What type of reaction is an ionisation reaction?
- Endothermic
- Energy required to put in
What is proof of electron orbitals?
- Difference in ionisation energies to remove an electron
Why is the ionisation energy for the final electron in a shell less?
- furthest from nucleus
- attraction weaker due to shielding
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What do successive ionisation energy show?
- greatest jump between the ionisation energy show that electron is being removed from further position to the nucleus
- if the jump is greatest between the 4th and 5th electron therefore the element is group 4
What are electron densities?
- Spread around the nucleus like a cloud
- Shows where the electron is most likely to be
- darker areas show a greater chance of an electron present
- p sub shell is spherical
- d sub shell are dumbells at right angles
What is electron spin?
- Electrons can spin clockwise or anticlockwise in an orbital
- Two electrons cannot have the same spin due to repulsion
What is periodicity?
- Repeating patterns in the periodic table
- They are repeating properties
- Similar for boiling points, ionisation energies and atomic radius
What is the trend of atomic radius for the periodic table
- Down a group - Increases - Due to more electrons shells therefore more electron shielding so attraction is less
- Across the period- Decreases- Increasing number of nuetrons therefore greater positivity of the element. Due to same shell, held more tightly
Explain the trend in ionisation energy for a period?
- Increase across a period- Increases positive charge without any extra electron shells therefore smaller radius so greater attraction beween the electron and nucleus
- Decreases down a group- More electron shells therefore more shielding therefore the attraction between the electron and the nucleus is less so less energy
What three factors affect ionisation energy?
- Attraction between the nucleus and the outermost electron
- Size of the positive nuclear charge
- Extent of shielding
What is the trend in melting temperature for a period?
- Group 1-3 - Increases due to more electrons increasing the strength of the bonds - metallic structure
- Group 4- Strong covalent bonds leading to very high melting temperatures- giant molecular structure
- Group 5-8- Simple molecules so low temperatures
What affects melting temperatures?
Type of bonding and structure
