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Atomic Structure & Periodic Table
Atoms introduction
Electronic structure
brings you
back here.
end
THE PARTICLES
IN THE ATOM
Number of
protons
and
Small
central
electrons
nucleuswill
always be equal
the of an
in aninatom
nucleus
element.
So overall, they
have no
In shells
around
electrical
the
atom
charge.
mass
charge
proton
1
+1
neutron
1
0
electron
-1
Atoms of different elements have different numbers
of protons
proton
number
Any atomThe
with
Nitrogen
proton
6 protons
atoms
number
in have
the
of nucleus
neon
7 protons
is 10.
must be carbon.
The mass
The proton number is sometimes
called
the atomic
number
is the
total number.
number of
It is the number of protons present in
neutrons
in an atom.
the nucleus of an atom.
mass number
(protons + neutrons)
Proton number
14
6
C
protons &
So this atom of carbon has :
6 protons
(14 – 6) = 8 neutrons.
6 electrons
to make the atom
electrically neutral
ISOTOPES.
These are atoms of the same element with
different numbers of neutrons
Chlorine has two different isotopes
35
17
Cl
37
17
Cl
17 protons
17 electrons
(35 – 17) = 18 neutrons
17 protons
17 electrons
(37 – 17) = 20 neutrons
same number of protons
same element.
different numbers of
neutrons
ELECTRONS
occupy particular energy levels (“shells”)
around the nucleus of the atom.
The electrons in an atom will always occupy the lowest
available energy levels.
The innermost shells closest to the nucleus will fill up
first, as atoms contain more electrons.
If an atom has more than 10
electrons, electrons start to fill
the third shell out.
2
max
8
max
8
max
the second shell can contain
eight
electrons,
Once
the third maximum.
shell has eight
electrons, the fourth shell starts
If an atom has more
to fillthan 2
electrons, electrons start to fill
this next shell out.
So more than 18 electrons in the
the
atom,
lowest
means
energy
thelevel
fourth
can
shell begins
contain
to only
be occupied
two electrons.
by electrons.
shell full
x
xx
16
8
x
O
xx
x
The
In the
electronic
shells :structure
8 electrons
is 2(x)
:6
x
shell full
shell full x
shell full x
x
x
x
x
x
x
x
xx x
x x x
x
x
In the nucleus :
8 protons
8 neutrons
xx
39
19
K
In the nucleus :
19 protons
20 neutrons
In the shells
: 19 electrons
The electronic
structure
is 2 : 8 : (x)
8:1
THE PERIODIC TABLE.
Group
Group
7 0
The elements in this table are the “building
NON-METALS
blocks” of all
materialsGroup
Group
Group
Group
Group
Group
METALS
H
He
3 4 5 6
1 2
Li Be
Na Mg
K Ca
Elements in this central block are
known as TRANSITION METALS.
Cr
Fe
C N O
Al
Ne
Cl Ar
Ni Cu Zn
The 100 chemical elements can be arranged in order of their
increasing atomic numbers in horizontal rows.
-- watch
appear in order
of increasing
of
This
listthem
is arranged
so that
elementsnumbers
with similar
chemical
protons
in the nuclei
of their
properties
come
in atoms.
vertical columns together.
These are GROUPS.
Properties are similar but there is a gradual change in the
properties of a group as you go from the top to the bottom
PERIODIC TABLE WITH THE FIRST 20 ELEMENTS.
1
H
1
3
THE ATOMIC (PROTON) NUMBER IS ABOVE EACH SYMBOL
2
THE ELECTRONIC
STRUCTURE IS BELOW
EACH SYMBOL
2
4
5
6
7
8
9
10
He
Li
Be
B
C
N
O
F
Ne
2:1
11
2:2
12
2:3
13
2:4
14
2:5
15
2:6
16
2:7
17
2 :8
18
Na Mg
Al
Si
P
S
Cl
Ar
2:8:1
2:8:3
2:8:4
2:8:5
2:8:6
2:8:7
2:8:8
2:8:2
19
20
K
Ca
2:8:8:1 2:8:8:2
The The
halogens
in
group
71
allall
have
seven
electrons
in their
metals
The
noble
in
group
gases
in
have
group
one
0third
all
electron
have
inlevel
Here,
across
the
second
period,
the
second
Here,
across
the
third
period,
the
energy
outermost shells.
The
other
two
halogens that come
full
their
outermost
electron
shells
shells.
energy level
is outer
gradually
filling
with electrons
is gradually
filling
with
electrons
below
fluorine
&
chlorine
are
bromine
anddon’t
iodine.
This gives them stability & explains why they
react.
1/--страниц
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