CHEMISTRY1 AS LEVEL Flashcards
Relative isotopic mass
The mass of an atom of an isotope compared with 1/12th of the mass of an atom of carbon-12.
Relative atomic mass
The weighted mean mass of an atom of an element compared with 1/12th of the mass of an atom of
carbon-12.
Calculate atomic mass
Ar = total mass of atom/ number of atom
Relative molecular mass
Average mass of a molecule relative to 1/12th of the mass of an atom of carbon-12.
Relative formula mass
Weighted mass of a formula unit compared to 1/12th of the mass of an atom of carbon-12.
Principles of mass spectrometers
- Form ions from sample
- Ions seperated
- According to Mass to Charge ratio (m/z)
- Ions detect
How mass spectrometry can be used to…?
- Provide structural information
- Identify unknown compound
- Determine the relative abundance of each isotope of an element
Step 1. Ionization
- Sample dissolved in a volatile solvent (vaporize easily)
- vaporized solvent forces through a hollow needle
- connected to the +ve terminal of a high-voltage supply - PRODUCE POSITIVELY CHARGED DROPLETS /ION
Step 2. Acceleration
- POsitive ions are attracted toward a magnet
- The magnet is negatively charged and causes the ions to accelerate [all ions have the same KE]
–> Therefore, the heavier, larger particles will have a lower speed
Step 3. Deflection
Separate isotopes according to Mass/charge ratio
Step 4. Detection
WHen the ions arrive at the detector, their flight time is recorded.
- At the detector, the positive ions pick up an electron, causing a CURRENT TO FLOW
Step 5. Data analysis
The detector passes a signal to the computer- generating a mass spectrum
Isotopes
Atoms with the SAME number of protons and DIFFERENT numbers of neutrons.
covalent bond
The covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded pair.
Trends in electronegativity
Electronegativity increases:
1) Across a period
2) Up a group
Polar bond
Occurs when one of the atoms in a bond has greater electronegativity than the other - creating a difference in electronegativity
Electronegativity
Ability to attract shared pair of electrons towards itself
DIPOLE
The differing attraction for the pair of electrons allows there to be a small charge difference between the atoms
: Permanent dipole - charge difference allows present
Electron density
The electron density relates to the probability of finding electrons at a particular position in space
: cloud of electrons around the nucleus
