Transcript Atoms and Elements

Atoms
Chapter 4
Atomic Theory & Structure
Definition of the Atom
• Remember, Democritis defined “atomos”
as the SMALLEST, INDIVISIBLE part
of matter that still had physical and
chemical properties?
• Democritus was wrong! Atoms CAN BE
DIVIDED INTO SMALLER PARTS!!!
Modern Definition of the Atom
• John Dalton
• Atomic Theory
• 1. Atoms are the smallest part of
matter that RETAINS PROPERTIES.
• 2. All atoms of an element are the
same.
• 3. Atoms of different elements can
join to form compounds.
Parts of an Atom
• Nucleus - inside
• Made of
– Protons (positive)
– Neutrons (neutral)
• Electron Cloud - outside
• Made of
– Electrons (negative)
• Same number of protons
and electrons! (Same
number of positives as
negatives!!)
If the protons & electrons are the same
in every atom the same element….
• …then what is the charge of a typical atom?
• 2 protons & 2 electrons
• +2 + (-2) = 0 NEUTRAL!!
• Atoms are typically neutral or they have no charge!
Orbits in the Electron Cloud
• Electrons orbit the nucleus
in “rings” or energy levels.
• Notice how the electrons
orbit the nucleus in many
different dimensions.
Remember, the atom is
3D!
The Nucleus is the Heaviest Part…
• The Neutrons and Protons
are VERY HEAVY!!
– They are made of even
smaller part called
QUARKS.
• The Electrons are so small
they are almost
WEIGHTLESS!!
• The “Rings” don’t actually
exist, they are just drawn in
the picture to illustrate the
path of the orbits.
Energy Levels or “Rings”
• For our purposes, there are
four rings around the nucleus.
• The closest ring holds
2 electrons.
• The second ring holds
8 electrons.
• The third ring holds
8 electrons.
• The fourth ring holds
2 electrons.
Review: STORYTIME!!!
• Let’s hear a story about the ….
ATOMS FAMILY!!
http://youtu.be/Q9Pt6WZpTxU
Something to Think About…
• What is the difference
between an atom and a
cell?
• Cells are the smallest
LIVING things. Atoms are
the smallest part of
EVERYTHING and they
are not alive!