by Ele
, the periodic table
d 8
& ③ A B b f
b B B d d now
'
I Ll relative atomic mass chemical
symbol
^
hydrogen
atomic 1
name
number
.
in 1869 , Dmitri Mendeleev arranged SO known elements in order of atomic mass to make a Table of Elements.
Mendeleev s table placed elements with similar chemical properties in the same vertical groups - but he found
÷
that he had to leave gaps in the table to make this work. The gaps predicted the properties of undiscovered
elements. Since then new elements have been found and they fit into the gaps.
there are ish elements that all materials are made of, with more still being discovered.
the modern periodic table shows the elements in order of increasing atomic number.
-
the periodic table is laid out so that elements with similar properties form columns.
I
these vertical columns are called groups.
/
the group to which an element corresponds to the number of electrons it has in its outer shell (group I elements
.
have I outer shell electron, group 2 elements have 2 outer shell electrons and so on).
.
some groups have special names, group I elements are called alkali metals, group 7 elements are called halogens,
group O are called the noble gases.
the rows are called periods. The properties of elements change as you go along a period (sometimes dramatically)
: elements in one group all have the same number of electrons in their outer shell, that is why they have similar
properties and why we arrange them this way. The properties of elements depend on the number of electrons they
have. Atomic number is very significant because it is the number of electrons each atom has But it is the number
of electrons in the outer shell which matter.
, the periodic table
d 8
& ③ A B b f
b B B d d now
'
I Ll relative atomic mass chemical
symbol
^
hydrogen
atomic 1
name
number
.
in 1869 , Dmitri Mendeleev arranged SO known elements in order of atomic mass to make a Table of Elements.
Mendeleev s table placed elements with similar chemical properties in the same vertical groups - but he found
÷
that he had to leave gaps in the table to make this work. The gaps predicted the properties of undiscovered
elements. Since then new elements have been found and they fit into the gaps.
there are ish elements that all materials are made of, with more still being discovered.
the modern periodic table shows the elements in order of increasing atomic number.
-
the periodic table is laid out so that elements with similar properties form columns.
I
these vertical columns are called groups.
/
the group to which an element corresponds to the number of electrons it has in its outer shell (group I elements
.
have I outer shell electron, group 2 elements have 2 outer shell electrons and so on).
.
some groups have special names, group I elements are called alkali metals, group 7 elements are called halogens,
group O are called the noble gases.
the rows are called periods. The properties of elements change as you go along a period (sometimes dramatically)
: elements in one group all have the same number of electrons in their outer shell, that is why they have similar
properties and why we arrange them this way. The properties of elements depend on the number of electrons they
have. Atomic number is very significant because it is the number of electrons each atom has But it is the number
of electrons in the outer shell which matter.
