C3: Periodic Table

Hey, here is a document mainly for students taking AQA Triple Science but it may help others too. This has information from the C3 (chemistry) section about the periodic table and the previous periodic tables and how they were classified. I hope this helps you to revise! Please rate and comment on how to improve :D

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  • Created on: 07-04-10 18:31
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C3: The Periodic Table
The periodic table was developed to classify elements before
atomic structure was understood.
It is a powerful aid to understanding the properties and reactions
of the elements.
Early Attempts to Classify the Periodic Table
Newlands, and then Mendeleev, attempted to classify the
elements by arranging them in order of their atomic weights.
The list can be arranged in a table so that elements with similar
properties are in columns, known as Groups.
The table is called a periodic table because similar properties
occur at regular intervals.
The early periodic tables were incomplete and some elements
were placed in inappropriate Groups if the strict order of atomic
weights was followed.
Mendeleev overcame some of the problems by leaving gaps for
elements that he thought had not been discovered.
When electrons, protons and neutrons were discovered early in
the 20th century, the periodic table was arranged in order of
atomic (proton) numbers. When this was done, all elements were
placed in appropriate groups.
The Modern Periodic Table
The modern periodic table can be seen as an arrangement of the
elements in terms of their electronic structures.

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Elements in the same Group have the same number of electrons
in their highest occupied energy level (outer shell).
The trends in reactivity within Groups in the periodic table can be
explained because the higher the energy level:
the more easily electrons are lost
the less easily electrons are gained.…read more

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The elements in Group 7 of the periodic table (known as
halogens):
have coloured vapours
consist of molecules which are made up of pairs of atoms
form ionic salts with metals in which the chloride, bromide or
iodide ion (halide ion) carries a charge of ­1
form molecular compounds with other nonmetallic
elements.
In Group 7, the further down the group an element is:
the less reactive the element
the higher its melting point and boiling point.…read more

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Many transition elements have ions with different charges, form
coloured compounds and are useful as catalysts.…read more

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Newlands and Mendeleev, have led through
the growth of chemical knowledge to the modern periodic table
· to explain why scientists regarded a periodic table of the
elements
first as a curiosity, then as a useful tool and finally as an important…read more

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