Transcript Atoms1

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This is a block of GOLD
Being an ELEMENT, it
is a PURE substance,
so it contains particles
of only ONE kind …
GOLD
ATOMS
An atom is the smallest particle of an
element that can exist.
Cut a diamond up with a “magic knife”
until you have the smallest piece
possible, and you have a ….
CARBON ATOM
Let’s look at the atom in more detail…..
In the middle
are larger
particles in
the
NUCLEUS
…and there
are some
tiny particles
spinning
round it in
ORBITS
It’s made up of even smaller
This is an atom of HELIUM.
particles!
Let’s “freeze” the action and take a closer
look at these sub-atomic particles…
These are PROTONS
These are NEUTRONS
These are ELECTRONS
A PROTON is positively
charged, and has the same
mass as…
..a NEUTRON, which has no
charge.
An ELECTRON is negatively
charged, but has a mass less
than 1/2000 of that of either
of the other particles!
Looking at the Helium atom again,
let’s see how many of each subatomic particle there are…
2 protons and 2 neutrons make up the
nucleus. Together, let’s say they have a
mass of 2 + 2 = 4
Two protons means 2 positive charges
…and two electrons means 2 negative charges.
…so that’s +2 -2 = 0 , so there’s no overall
electric charge on the atom!
A helium atom is a typical atom, so we
can say the rules are….
Number of protons
+
= “Mass number”
Number of neutrons
Number of protons
(is equal to)
= “Atomic Number”
Number of electrons
…so for Helium, that’s…
Mass number 4
He
Atomic number 2
Let’s look at carbon
again…
There are 6 protons,
so there must also be
6 electrons.
That makes its atomic
number to be 6
6 protons and 6 neutrons
means its mass number
is 12
…so we’ve got…
12
6
C
Time for you to get some practice in!
Fill in the gaps in this table:
Name
Symbol
Hydrogen
Mass
No.
Atomic
No.
protons
neutrons
1
Li
1
3
Potassium
4
19
Beryllium
20
5
Ca
40
Iron
30
Boron
6
Ne
35
4
20
26
Cl
electrons
17
10
10
5
Extension: Look at your periodic table.
Fill in a similar table for :
• the alkali metals (down to rubidium),
• the alkaline earth metals (down to calcium),
• the halogens (down to iodine) and
• the inert gases (down to xenon).
Can you see any patterns?
Did you get it right?
Name
Symbol
Mass
No.
Atomic
No.
protons
neutrons
electrons
Hydrogen
H
1
1
1
0
1
Lithium
Li
7
3
3
4
3
Potassium
K
39
19
19
20
19
Beryllium
Be
9
4
4
5
4
Calcium
Ca
40
20
20
20
20
Iron
Fe
56
26
26
30
26
Boron
B
11
5
5
6
5
Chlorine
Cl
35
17
17
18
17
Neon
Ne
20
10
10
10
10
A October
presentation
2005by
R. G.end
Smith