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Elements of life notes for Salters Advanced Chemistry B
First year notes for chapter one - elements of life. Everything you need to know explained in a very good way, not just copied from the textbook.
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Chapter 1 - Elements of Life, EL 1 - Where do the chemical elements come from?
Nuclear fusion
● The joining of two or more nuclei to produce a single, larger,
more massive nucleus
● New nucleus is a new element
● Large amounts of energy are released during this process
Nuclear equations
● These are equations using the nuclear symbol (mass at the top
charge at the bottom
The Big Bang Theory
● All matter contained in a single point
this then underwent an explosive expansion (the big bang).
● After 3 minutes, the nuclei of hydrogen and helium formed.
● After 10,000 years, the universe cooled enough so electrons
could be caught by protons and atoms of hydrogen and helium
were formed.
● Universe continued to cool and gas and dust were pulled
together by their gravity forming gas clouds.
● Parts of the clouds contracted in on themselves which
compressed the gas forming clumps of denser gas. This is at
the center where temperatures are hot and the atoms could
not keep their electrons.
● The denser gas areas then became a plasma of ionised atoms
and unbound electrons.
● Nuclear reactions occur creating a lot of energy causing the
cloud to glow and become a star.
● Nuclear reactions create hot winds which drive away some dust
and gas leaving just the star. Planets condense out of the
remaining dust cloud around the star.
● Nuclear fusion is common in the center of stars. Extreme
conditions are needed for fusion to happen, but a lot of energy
is made and it produces no pollution. So it is currently being
researched for a useful source of energy.
All stars turn hydrogen into helium by nuclear fusion.
, Heavyweight stars - other fusion reactions take place, as well as
hydrogen fusion, creating heavier elements than helium. Eventually,
the core is iron when iron atoms fuse together they absorb energy
rather than releasing it. This makes the core unstable and it
explodes (supernova). Supernova causes the elements to be
dispersed into dust and gas, so the cycle starts again.
Lightweight stars - (e.g. the sun) they are not as hot and will last
longer than heavyweight stars, they will keep shining until all of the
hydrogen has been used up. Once the hydrogen is used up they will
expand into a red giant, as it gets bigger the outer gasses drift off
leaving a white dwarf about 1/100th the size of the original star.
The atom (basics)
Particle Mass on Charge Location in the Nuclear symbol
relative atomic atom
mass scale
Proton 1 1 In nucleus 1
+1 H
Neutron 1 0 In nucleus 1
0n
Electron 1/2000 ≈ 0 -1 Around nucleus 0
−1 e
The atomic number (Z):
● Number of protons in the nucleus which is equal to the charge
on the nucleus.
● Same for every atom of an element e.g. Z = 6 for all carbon
atoms.
The mass number (A):
● Number of protons and neutrons in the nucleus.
● Mass number (A) = atomic number (Z) + number of neutrons (N)
Mass spectrometry
Mass spectrometry measures the atomic mass of different particles
in a sample and the relative abundance of different isotopes in an
element.
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