Test 1 Flashcards
Chadwick
Discovered neutrons
John Dalton
Cannot destroy atom
Distinct masses and properties
JJ. Thompson
Proposed the convept of electrons
Rutherford
Stated atoms consist of a positively charged nucleus (it is dense and contains all the mass)
Niels Bohr
Proposed that atoms are restricted to a circular orbit
Schrodinger
Proposed that electrons are found in clouds (orbitals)
Description of metals
Grey solid
Description of mercury
grey liquid
Description of gold
Yellow solid
Description of copper
Salmon pink solid
Isotopes
Atoms of the same element with same number of protons but different number of neutrons
Similarities and Differences of isotopes
Similarities: Same number of protons, same chemical properties (reactivity, heat conduction, stability)
Differences: Number of neutrons, different physical properties (BP/MP/Density/Radioactivity)
Orbital
Region around the nucleus of an atom that can hold up to 2 electrons with opposite spins
Element
Simplest kind of substance that cannot be broken down into anything simpler
Compounds
Substances made of 2 or more different elements chemically bonded together
Molecule
Particle containing 2 or more different elements chemically bonded together
Atom
Smallest particle of element that can exist on its own
Ion
atom/atoms with a positive or negative charge from gaining or losing electrons
Empirical Formula
Simplest whole number ratio of a compound/element
Electronegativity
The ability of an atom to attract bonding pair of electrons
Limitations of flame test
- Multiple elements exhibit similar colours
- Colour assessment is subjective between individuals
- Emitted phons may lie outside visible light spectrum
AES
Qualitative atomic analysis to identify the identity of a metal ion
AAS
Quantitative and qualitative atomic analysis to identify the concentration of known metal ions
Relative atomic mass
Mass of an atom compared to the mass of 1/12 of a carbon 12 atom
Mass Number
The sum of protons + Neutrons
How to mass spectrometry help calculate the isotopic composition of an element
Sample of element is taken and vapourised using a heater/laser.
An electron gun is then used to knock electrons out of the atom to form positively charged ion.
Using electrostatic plates, the ions are then accelerated.
An electromagnet is then used to deflect these ions. Heavier particles deflect less, and lighter particles deflect more.
Ions are collected and the current is measured by the detection plate, to give the number of ions of each mass to charge ratio.
The electromagnet intensity is adjusted to find the abundance of different isotopes.
Flame test
Qualitative analysis to identify the identity of a metal ion
Energy levels
Electrons exist in different principle quantum levels e.g. (n=1, n=2, n=3). The cannot exist between principle quantum levels
How are flames tests used to identify elements
Electrons can be excited by heat. A salt is mixed with ethanol, and the ethanol is lit by a match. The heat from the flame excites the electrons of the metal ions in the salt. These electrons jump principle quantum levels when excited, however, the atom cannot remain stable. So the the electrons return to ground state, and in the process they emit photons at characteristic frequency (light). Combination of frequency gives of 1 visible light, which can be matched to known samples.
How is AAS used to identify different elements.
AAS uses the absorption spectra. A substance sample is vapourised and a light that matches the frequency of the substance you are looking for shines into the gas. If the light is absorbed, the elements present, and the concentration can be identified by however much of the light is absorbed.
Pros and cons of AAS
pros: useful for identifying metals in water, or smaller samples
cons: does not work for organic compounds
