Zusammenfassung der Ressource
Chemistry
- Atoms, Compounds and Isotopes
- The mass
number - total
number of
protons and
neutrons.
- Atoms of the same element all
have the same number of
protons - so atoms of different
elements will have different
numbers of protons.
- The atomic
number - number
of protons
- The atomic number tells you
how many protons there are.
- To get the number of
neutrons , just subtract the
atomic number from the
mass. electrons arent
counted in the mass
number because their
relative mass is very small.
- Isotopes are :
different atomic forms
of the same element ,
which have the same
number of protons but
a different number
neutrons.
- Compounds are formed when
atoms of two or more
elemements are chemically
combined together.For example ,
carbon dioxide is a compound
formed from a chemical reaction
between carbon and oxygen.
- Its difficult to
seperate the two
original elements
out again.
- Ionic Bonding
- In ionic bonding , atoms
lose or gain electrons to
form charged particles (
called ions ) which are
then strongly attracted
to another ( because of
the attraction of
opposite charges, + and
- ).
- All the atoms over the left hand side of the
periodic table, e.g. sodium, potassium ,
calcium etc. have just one or two electrons in
their outer shell ( highest energy level ) . They
try to have the same electronic structure as a
noble gas. So given half the chance they do
get rid , and that leaves the atom as an ion
instead.
- On the other hand of the periodic
table , the elements group 6 and 7 ,
such as oxygen and chlorine, have
outer shells which are nearly full. The
sodium gives up its outer electron and
becomes an Na+ ion. The chlorine
atom has picked up the spare electron
and becomes a cl- ion.
- Ions and Formulas
- Electrical structure of ions
- Covalent Bonds
- Metallic structures