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AS
UNIT CH1 ­ Controlling and Using Chemical Changes (in order to make things,
produce energy and solve environmental problems)
Preamble
This unit begins with some important fundamental ideas about atoms and the use of
the mole concept in calculations.
Three key principles governing chemical change are then studied, viz. the position of
equilibrium between reactants and products, the energy changes associated with a
chemical reaction and the rate at which reactions take place.…read more

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UNIT CH1 Controlling and Using Chemical Changes (in order to make things,
produce energy and solve environmental problems)
TOPIC 1
1.1 Basic ideas about atoms
1.2 Chemical calculations
TOPIC 2
2.1 Chemical eqilibria and acid-base reactions
2.2 Energetics
2.…read more

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Basic ideas about atoms
Topic 1.1 (a)
Learning Outcome: Describe electrons, protons and neutrons in terms of their
relative charges and masses, and the distribution of charges and masses within
atoms.
Atomic Structure.
Atoms are made up of three fundamental particles, the proton, the neutron and the
electron.
electrons surrounding
the nucleus
most of the
volume of the the nucleus made up of
atom is empty protons and neutrons.
space This is where nearly all
the mass of the atom is.…read more

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Topic 1.1 (b)
Learning Outcome: understand the terms atomic number, mass number and
isotope, and the connection between atomic numbers and mass numbers.
The number of protons in the nucleus of an atom is called the atomic number (Z).
Each element has its own atomic number.
For example hydrogen has atomic number 1.
Lithium has atomic number 3.
Chlorine has atomic number 17.
The number of protons plus the number of neutrons is called the mass number
(A).…read more

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Topic 1.1 (c)
Learning Outcome: deduce, given atomic and mass numbers, the numbers of
protons, neutrons and electrons in specified isotopes;
35 37
Taking the isotopes above, 17 Cl and 17 Cl , we can deduce the numbers of electrons,
protons and neutrons in each neutral atom.
mass number(A) =
number
atomic number(Z) = number of number of
isotope of
number of protons protons plus electrons
neutrons
neutrons
35
17 Cl 17 35 18 17
37
17 Cl 17 37 20 17
Topic 1.…read more

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Topic 1.1 (e)
Learning Outcome: describe the nature of alpha () and beta () particles and of
gamma () radiation and recall their behaviour in electrical fields and their relative
penetrative powers.
Radioactive isotopes
Some isotopes are unstable; these are usually, but not always, heavy nuclei like
those of uranium and plutonium.
The nuclei of radioactive isotopes spontaneously disintegrate and emit either alpha
() particles (which are helium nuclei) or beta () particles (which are electrons).…read more

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Topic 1.1 (f)
Learning Outcome: describe and explain the changes in mass number and atomic
number resulting from alpha () and beta () emission
It is important to note that these radiations come from the nucleus of the atom.
This means that alpha () and beta () radioactive emissions result in the formation
of a new nucleus with a new atomic number and the product is a different element.
radiation reduces the energy of the nucleus.…read more

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Topic 1.1 (g)
Learning Outcome: describe the adverse consequences for living cells of exposure
to - radiation and to - and - emitters;
We all receive radiation which is called background radiation, arising from naturally
occurring radioactive sources, man-made radiation and radiation reaching the Earth
from space.
APPROXIMATE TOTAL YEARLY RADIATION EXPOSURE IN THE UK
Average annual dose to the UK population from all sources, 2.…read more

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It is known that exposure to radiation can cause cell mutation leading to carcinomas
and to forms of leukaemia. Even small increases in the background level of radiation
may have significant effects on the population as a whole. This is because the
probability for cell mutation is higher when applied to a large population sample.…read more

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