Elements of Life Revision Notes

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Elements Of Life Revision Notes
Elements of Life
All elements are made up from atoms. Atoms are made up of protons, neutrons and
electrons. There are the same number of electrons as there are protons.
The mass number tells you the total number of protons and neutrons, whereas the atomic
number tells you the number of protons (electrons) in the atom.
Ions are atoms with a different charge due to the loss or gain of electrons. A positive ion has
lost electrons, and a negative ion has gained electrons.
Isotopes are atoms of the same element, with a different mass number but the same atomic
number. Isotopes have the same chemical properties, but different physical properties.
Ancient Greeks indivisible particle
Dalton Solid Spheres
JJ Thompson Plum Pudding Model (positively charged sphere with electrons embedded)
Rutherford Gold Foil Experiment = tiny + nucleus, surrounded by sea of electrons, most of
atom is empty space
Moseley Charge of nucleus increased from one element to another, in units of one.
Rutherford Discovered protons
Chadwick Neutron
Bohr Model = Electrons only exist in fixed shells; each shell has fixed energy; Electron moves
shells - electromagnetic radiation absorbed or emitted; radiation will have a fixed frequency.
A mass Spectrometer can be used to tell you the relative mass and the molecular structure of
a molecule.
1) Vaporisation ­ Sample is turned into gas.
2) Ionisation ­ gas particles bombarded with high-energy electrons; electrons knocked off =
positive ions.
3) Acceleration ­ the positive ions are accelerated by and electric field, lighter the ion, the
faster it goes.
4) Detection ­ time taken for the positive ion to reach the detector is measured.
A Mass Spectrometer turns the information into a graph. If the sample is an element, each
line will represent a different isotope of the element.
% Relavtive Isotopic Abundance =total relative abundance
relative abundance ×100%
Bombarding molecules with electrons can break it up into fragments, these show up on the
mass spectrum making a fragmentation pattern. You can use fragmentation patters to
identify molecules and their structure.
If an atom is unstable it will break down to become stable. This breaking down is called
radioactive decay. Alpha, beta or gamma radiation can be emitted.
Alpha () Particles Beta () Particles Gamma () Rays
What they are Helium Nuclei (24 He) Electrons (-10e) Very short
electromagnetic waves
Penetrating Power Stopped by Paper Stopped by Stopped by Lead
Aluminium
Ionising Ability Strong Moderate Weak
Deflection in electric Slight Large Not Deflected
field
Half-life is the time taken for half the atoms in a sample to decay.

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Elements Of Life Revision Notes
Radioactive Isotopes can be used as tracers. An isotope with a long half-life is too dangerous
as the patient is exposed to radiation for a long time, and a short half-life is too inconvenient
as there is not enough time for the tracer to make their way around the body.…read more

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Elements Of Life Revision Notes
Ionic bonding is where electrons are transferred from one atom to another so that each atom
has a full outer shell. The atoms either lose or gain electrons, and this becomes ions.
Ionic crystals are giant lattices of ions. The structure is giant because it's made up of the same
basic unit repeated over and over again.
Ionic compounds conduct electricity when molten or dissolved, not when solid.
Ionic compounds have high melting points.
Ionic compounds often dissolve in water.…read more

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Elements Of Life Revision Notes
6 0 Octahedral 90
3 1 Trigonal Pyramidal 109
2 2 Bent 120
Mendeleev arranged the periodic table in order of proton number and left gaps for unknown
elements; he then predicted the properties of these unknown elements and was correct
when they were discovered.
Group 2 elements react with water to produce hydroxides, these increases down the group.…read more

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