summary on chemical peridicity

this is a summary of the key points needed for As chemistry on chemical periodicity.

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Early periodic patterns (regularly repeating
variations) in the properties of elements in order of
their relative atomic masses. The modern periodic
tables are based on the elements in order of their
atomic numbers.
A group in the periodic table contains elements with
the same outer-shell electronic configuration but
very different atomic numbers; the elements and
their compounds have many similar chemical
properties.
The elements in a block have their outer-most
electrons in the same type of sub shell. For example,
s-block elements have their outer most electrons in
an s subshell.
Periods in the periodic table are sequences of
elements, differing by one proton and one electron,
from group 1 to group 0.
Periodic variations may be observed across periods
in physical properties such as ionization energies,

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The main influences on ionization energies and
atomic radii are: the size of the positive nuclear
charge; the distance of the electron from the
nucleus; the shielding effect on outer electrons by
electrons in filled inner shells.
Ionization energies decrease down a group and tend
to increase across a period; atomic radii increase
down a group (effect of increased shielding) and
decrease across a period (effect of increased nuclear
charge).…read more

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Group 0 elements consist of individual
atoms.
Successive ionization energy data of an element may
be interpreted in terms of the position of the
element within the periodic table.
Data on electronic configurations, atomic radii,
electrical conductivity, melting points and boiling
points may be interpreted to demonstrate
periodicity.
Chemically, the elements change from reactive
metals, through less reactive metals and less
reactive non-metals to reactive non-metals. Group 0
contains the extremely unreactive noble gases.…read more

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Metal chlorides have giant ionic lattice structures
and ionic bonding. They are neutral with a pH value
in aqueous solution of 7 (or slightly higher).
Non-metal chlorides have simple molecular
structures with covalent bonding. They are acidic
with a pH value in aqueous solution of around 2.
Sodium and magnesium react with water to give the
aqueous hydroxides. Sodium reacts more vigorously
than magnesium.
Aqueous sodium hydroxide has a pH value of 12-14,
aqueous magnesium hydroxide has a pH of 9-11.…read more

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