Zusammenfassung der Ressource
GCSE AQA Chemestry unit C3 1.1-1.5 key points
- C3
1.1
- The periodic
table of elements
developed as
chemists tried to
classify the
elements. It
arranges them in
a pattern in
which similar
elements are
grouped
together.
- Newlands table
put the
elements in
order of atomic
mass but failed
to take account
of elements that
were unknown
at that time.
- Mendeleev's
periodic table left
gaps for the
unknown elements,
and so provided the
basis for modern
periodic table.
- C3
1.2
- The atomic
(proton)
number of
an element
determines
its place in
the periodic
table
- the number of
electrons in the
outer shell
(highest energy
level) of an atom
determines its
chemical
properties
- the group
number in
the
periodic
table
equals the
number of
electrons
in the
outermost
shell
- we can explain
trends in
reactivity as we
go down a
group in terms
of
- The distance between the
outermost electrons and the
nucleus
- the number of
occupied inner
shells (energy
levels) in the
atoms
- C3
1.3
- the elements in
group 1 of the
periodic table are
called the alkali
metals
- Their
melting
points and
boiling
points
decrease
going
down the
group
- the metals all react with water to
produce hydrogen and the alkaline
metal solution containing the
metal hydroxide
- They form 1+ ions in reactions to
make ionic compounds. these are
generally white and dissolve in water,
giving colourless solutions
- The reactivity of
alkali metals
increase going
down the group
- C3
1.4
- Compared with the alkali
metals, transition metals
have much higher melting
points and densities. They
are also stronger and harder
but are much less reactive.
- The transition metals do not react
vigorously with oxygen or water.
- a transition element can
from ions with different
charges, in compounds that
are often coloured.
- Transition elements and their
compounds are important
industrial catalysts.
- C3
1.5
- The halogens
all form ions
with a single
negative charge
in their ionic
compound with
metals.
- The halogens form
covalent compounds
by sharing electrons
with other non-metals
- a more reactive halogen can displace a less reactive
halogen from ma solution of one of its salts.
- The reactivity of halogens decreases
as you go down the group