Atomic Structure,Bonding, energetics Flashcards
Isotopes
Isotopes are atoms of the same element with a different no. of neutrons
- chemical properties of isotopes are similar
- physical properties are different (due to mass - changes BP & MP)
proof of electron orbitals
- Drop of ionisation energy between G5 & G6 is proof of electron orbitals.
- Oxygen has a lower IE than nitrogen
- There’s no difference between atomic radius & shielding, but there is more repulsion between a pair of electrons within an orbital so electrons in shared orbitals are easier to move.
Time Of Flight (TOF) mass spectrometry processs
1 - IONISATION
↳ vaporised gas is ionised via electrospray or electron
impact
2 - ACCELERATION
↳ The ions are accelerated by an electric field. (relies on particles being charged)
↳ all ions will have the same KE (velocity dependent on
mass)
3 - ION DRIFT
↳ ions drift through the chamber at different speeds under no electric field
4 - DETECTION
↳ Ions are detected by producing current on detection plate which creates a mass spectrum.
Trend in Ionisation energy across a period
- ↑Nuclear charge across period ∵ increase in atomic no.
- ↓ Atomic Radius
↳ atomic radius decreases slightly due to greater nuclear charge that pulls outer electrons closer - NO change in shielding effect ∵ same no. of electron shells
Trend in Ionisation energy across a group
- ↑ Atomic Radius
↳ greater distance between nucleus and outermost electron, decreased attraction. - ↑ Shielding effect
↳ greater no. of inner shells, ∴ greater repulsion so decreased attraction. - negligible nuclear charge increase
Factors affecting IE
Shielding -
The repulsion of an electron from inner shell electrons.
- more inner shells present, lower IE
Atomic Radius -
↑ atomic radius, lower IE, outer electron further from nucleus so weaker attractive pull from nucleus.
Nuclear Charge -
higher nuclear charge the higher the ionisation energy, stronger attraction to outer electrons.
How is Electrospray Ionisation done?
Sample is dissolved in solvent
- High voltage is applied
- High voltage removes proton from solvent and attaches it to sample
- X(g) —> XH⁺(g)
How is Electron Impact Ionisation performed
- Sample is vaporised
- Hit with electrons from electron gun
- The electrons knock off electrons from the molecule
- X —-> X⁺+ e⁻
(often causes fragmentation)
Electron Configuration of Transition Metals
1s²2s²2p⁶3s²3p⁶4s¹3d⁵ <— Chromium
1s²2s²2p⁶3s²3p⁶4s¹3d¹⁰ <—- Copper
+ When forming ions they lose their 4s electron first
Proof of electron sub-shells
- Drop of ionisation energy between G2 & G3 is proof of sub-shells.
- Beryllium has a greater ionisation energy than boron.
- Boron’s outer electron occupies a 2p sub-shell which increases atomic radius & it’s electron experiences more shielding from inner electrons ( both 1s² and 2s²electrons shield it)
Properties of Water
- Significantly higher boiling point than other hydrides
- Surface tension ( how strongly molecules are held to the structure of a liquid)
- H bonds exert a downwards force
- High Viscosity
- Density of ice lower than water because it freezes into regular lattice
structure that are further apart so more open structure =
less dense - solvent can dissolve simple alcohols and ionic compounds
Physical Properties of Metallic Structures
- Metals have high boiling & Melting points
- More delocalised electrons present, the higher the melting point of the metal.
- because greater electrostatic attraction so stronger bond
- Good conductors of heat & electricity because of delocalised electronns
- insoluble unless liquid metal.
Charge Clouds
- region where there is a high chance of an electron pair being present. / region of negative charge.
- Can contain either boning pairs or lone pairs
- Lone pair electron charge clouds repel more than bonding pair clouds
Great repulsion LONE - LONE
LONE - BOND
BOND - BOND
Lowest repulsion
<- VSEPR theory
Formation of temporary dipoles
Temporary dipoles are week intermolecular forces
- When two atoms come towards each other the electron CLOUDS repel each other
- causes sudden displacement of electrons to one side resulting in a temporary dipole.
- dipoles are constantly being created or destroyed.
ALL shapes of molecules: name,shapes & angles
Hydrogen bonding
Polar bond - H” F,N,O’
- Hydrogen has a high charge density (only 1 shell) so the “ hydrogen can be attracted by lone pairs of nearby N,O,F molecules
+ due to hydrogen bonding it means HF is the hydrogen halide with the highest boiling point.
