Transcript Elements, compounds, symbols and formula

Elements, compounds, symbols
and formula
We have already learned that...
 Elements are: a pure substance that cannot
be broken into simpler parts by ordinary
chemical means.
 There are 114 elements
 Compounds are:a pure substance made up
of two or more elements, chemically
combined in fixed proportions
 there are millions of known compounds
Examples of Elements and
compounds
Elements:
Compounds:
hydrogen
copper
uranium
water
copper (II) sulfate
plastic
Elements and Symbols
Scientists have
devised a ‘short
hand’ way of
naming elements
 these are called
chemical symbols
 hydrogen = H
 carbon = C
 calcium = Ca
 Many symbols are the first
letter of the
element…carbon
 others are the first two
letters, like calcium
 others use two prominent
letters like cadmium…Cd
 still others use latin, greek
or other language roots,
like copper Cu (cuprium)
Elements and Symbols
 Whatever the reason
 The newest of the
for naming an
element, the same
rules apply
 only one capital letter
 if the symbol is two
letters, it must be one
upper and one lower
case letter
synthetic elements
have three letters, Uub
for example
 eventually when
element 112 is named
it will be given a two
letter symbol
Compounds and formula
 Compounds also have
 CO2 = carbon dioxide
a short hand way of
naming them
 these are called
chemical formula
 H2O is a familiar
example
 C6H12O6 = glucose
 H2O2 = hydrogen
peroxide
 CuSO4 = copper (II)
sulfate
Chemical formula
Like symbols, formula
have certain rules for
their use.
 They always contain
the elements found in
the compounds
 they always show the
relative number of
atoms of each element
For example:
 H2O tells us many
things about water…
 the fact that it is made
up of hydrogen and
Oxygen
 the fact that there are
2x as many hydrogen
atoms as oxygen
atoms
Chemical Formula
 From this you should
be able to see why it is
so important to follow
the naming rules for
elements
 Because we know that
symbols (elements)
can never be two
upper case letters, this
must be Carbon Oxide
Use “CO” as an example  In fact it is called
carbon
monoxide,
a
Is this an atom of Cobalt or a
deadly gas!
compound of Carbon
Oxide?