Transcript Structure of the Atom

Structure of the Atom
Sections 17.1-17.4
Review
• Elements are made up of only one type of
atom.
• All elements are listed on the Periodic
Table.
• Each element is represented by its atomic
symbol.
Atomic Symbols
• Some symbols come from the elements
name.
– Example: C is for Carbon
• Others come from the element’s Latin
name.
– Example:
•Au is for Gold (aurum)
•Pb is for Lead (plumbum)
About Atoms
• Atoms are so small they can’t be seen with
visible light.
• Photographs of atoms can be seen by a
scanning tunneling microscope.
• The atom is actually made up of smaller
subatomic particles.
– Proton
– Electrons
– Neutrons
The Nucleus
• Nucleus contains protons and neutrons.
• The electrons can be found surrounding
the nucleus in the electron cloud.
• Electrons are very far away from the
nucleus.
• There is actually a lot of empty space
between the nucleus and electrons.
Subatomic Particles
Particle
Charge
Mass Compared to
an Electron
Actual Mass
Electron
-1
1
9.11 x 10-31
Proton
+1
1836
1.673 x 10-27
Neutron
0
1841
1.675 x 10-27
Isotopes
• The number of protons tells us the atomic
number of the atom.
• The mass number is the total number of
protons and neutrons in the nucleus.
• Atoms can have different numbers of
neutrons.
• Atoms that have different numbers of
neutrons are called isotopes.
Isotopes
•There are three known isotopes of
Hydrogen.
1
1
H
2
1
H
3
1
H
1 proton
1 proton
1 proton
0 neutrons
1 neutron
2 neutrons
What do these numbers mean?
Mass Number
7
3
Li
Atomic Number
How many protons does lithium have?
How many neutrons does lithium have?
Element Symbol
Atomic Mass
• The atomic mass is NOT the same as the
mass number.
• The atomic mass shown on the periodic
table is an average of all the isotopes of
that element.