The Atom

1
The Atom
2
What is an Atom?

• Atoms are matter. All matter is made of atoms.
  All solids, liquids, and gases are made up of
  these tiny particles.

3
How big is an atom?

• Its not how big an atom is its how small!
• Atoms are so small that in just one drop of water
  there are about six sextillion atoms!
• THATS
• 6,000,000,000,000,000,000,000 atoms

4
What is an atom made of?

• Once people though that the atom was the
  smallest particle of matter in the universe.
• However, scientists now know that atoms are made
  of even smaller parts.

5

• Atoms are made of electrons, protons, and
  neutrons.
• With over 100 different elements, its the
  number of these subatomic particles that make
  each element unique.

6
Its like this
Electron
Proton

Neutron
7
Its like this
Electron
Proton

Neutron

• Protons and neutrons are at the centre of the
  atom, called the nucleus.

8
Its like this
Fun fact Electrons move at 2200km/s
Electron
Proton

Neutron

• Electrons are found moving around the centre,
  like the earth around the sun.

9
Its like this
Electron
Proton ()

Neutron

• Protons have a positive charge

10
Its like this
Electron (-)
Proton ()

Neutron

• Electrons have a negative charge

11
Its like this
Electron (-)
Proton ()

Neutron (0)

• Neutrons have a no or zero charge

12
Subatomic particle Charge Mass in grams Mass in AMU
Proton 1 1.673x10-24 g 1.007amu
Neutron 0 1.675x10-24 g 1.008amu
Electron -1 9.1x10-28 g 0.00055amu
13
Electrons

• Electrons are always moving
• They spin and move in any direction so long as
  they stay in their shell.
• The shell or orbital is the distance from the
  nucleus that an electron can move.
• Scientist use letters to name these shells.

nucleus
k
l
m
n
o
p
q
14
Holds two electrons
nucleus
k
l
m
n
o
p
q
Holds eight electrons
Holds eight electrons for the first 18 elements
and 18 electrons for others
15
Please note

1. Protons and neutrons have almost the same mass
2. Electrons are 2000 times lighter than protons and
   neutrons
3. Protons and electrons carry charge of equal
   magnitude.

16
How many protons, neutrons, and electrons are
there in an atom?

1. Atoms in their natural state have no charge
2. Neutral atoms have equal amounts of protons and
   electrons.
3. If an atom has more protons than electrons it is
   positively charged and vice versa negatively
   charged. These are called ions.

O2-
17
O2-

• In this example, oxygen has two more electrons
  than protons. How many electrons are there?
  (hint atomic number equals number of protons).

18

1. The number of protons identifies the atom.
   Number of protons equals atomic number.
2. Atoms of the same element that have the different
   number neutrons are called isotopes.

19
Determining the number of neutrons

• We can determine the number of neutrons by
  looking at the atomic mass
• We know that the mass of an atom is made up of
  mostly protons and neutrons.