AS Chemistry Unit 1 Notes

AS CHEM1 Notes

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  • Created by: Mariam
  • Created on: 26-04-14 14:01
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Mass Spectrometry
-A device that enables us to identify substances by working out their masses
-Has 5 Stages:
1. Vaporisation: Makes atoms easier to ionise
2. Ionisation: Atoms are blasted with a high energy electron gun which removes one electron from the outer shell of each atom Al(g) Al (g) + e¯
3. Acceleration: Positively charged ions are accelerated using negatively charges electrodes/magnetic plates Providing all atoms with the same Kinetic Energy
4. Deflection: Strong/Changing magnetic field is used to deflect particles around the bend The lighter the atom the more it is deflected
5. Detection: Ions produce a tiny electrical current when they're hit the detector The larger the abundance of an isotope the more intense the current
Interpreting the Mass Spectrometer
-The bigger the peak on the chart the more abundance there is of that particular isotope
Electron Configuration:

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Ionisation energies…read more

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Evidence for Energy Levels
First Ionisation Energies INCREASE across a PERIOD
1. Atomic Radius stays the same so electrons are being moved from the same shell Same level of shielding across the period
2. Nuclear charge increases due the increase of protons Increased pull from nucleus
First Ionisation Energies DECREASE down a GROUP
1. Atomic Radius increases Electrons are further from the nucleus so they experience a reduced nuclear pull
2.…read more

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Melting and boiling points increase because there are more electrons being delocalised into the giant metallic structure Greater electrostatic forces of
attraction between positive ions and delocalised electrons
Group 4 Giant Covalent:
Silicon atoms are covalently bonded throughout in a giant covalent structure Difficult to melt or boil due to strong covalent bonds
Group 5-7 Simple Covalent & Group 0 Separate Atoms
Melting and boiling points depend on the amount of van der waal forces which depends on the size of the molecule Larger molecules…read more

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Ionic Bonding:
-Happens between oppositely charged ions in a lattice which are attached to each other by strong electrostatic forces of attraction
-Have high melting and boiling points
-Conduct electricity when molten
Covalent Bonding:
-Shared pair of electrons
-Simple covalents have very weak intermolecular forces so have very low melting and boiling points
-Giant covalents have strong covalent bonds so have very high melting and boiling points
Dative Co-Ordinate Bonding:
-Both electrons that are being shared some from the same atom
-Examples include:
Carbon…read more

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-The ability/power of an atom to withdraw electron density from a covalent bond
-Increases across a period
-Decreases down a group
-N,O and F are the most electronegative elements
-Attraction causes uneven/asymmetrical distribution of electrons causing the more electronegative atom to develop a slightly negative charge and the other a
positive charge This is a polar bond/Dipole moment
-Some molecules may have no overall dipole moment because the charges cancel out
Forces acting between Molecules:
-Intermolecular forces, starting with the strongest:…read more

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Hydrogen Bonding…read more

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Diapole-diapole Forces
3.…read more

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