Transcript Representing Atoms - Mrs. Lee's 8th Grade Science Page

REPRESENTING ATOMS
1. Atoms that are not bonded and stand alone are neutral.
2. That means in neutral atoms the number of protons are
equal to the number electrons.
This carbon atom is
neutral because it has 6
protons and 6 electrons.
The positive charge of the
protons “cancel out” the
negative charge of the
electrons.
• 3. Only a certain number of electrons can fit in each electron
shell (or level).
Energy
Level
1
2
3
4
5
6
Electron
Capacity
2
8
18
32
50
72
THE RULE OF OCTET
• Every atom tries to have 8 electrons in its outermost or valence shell. To
accomplish this, atoms may need to give up, share, or take electrons.
• Noble gases have complete outer electron shells, which make them very stable.
Other elements also seek stability, which governs their reactivity and bonding
behavior.
• Halogens (group 17) are one electron away from filled energy levels. They each
have 7 valence electrons so they are very reactive.
• Alkali Metals (group 1) are very reactive metals that do not occur freely in nature.
These metals have only 1 valance electron in their outer shell. Therefore, they are
ready to lose that one valance electron in ionic bonding with other elements.
• Alkaline Earth Metals (group 2) are also reactive metals that do not occur freely in
nature. These metals have 2 valance electrons in their outer shell.
4. The atomic number on the periodic table tells us how
many protons each atom of the element has.
5. You can represent an atom by beginning with the atomic
number. Let’s represent an Aluminum atom.
Aluminum
Al
13
26.98154
To find the number of
neutrons, subtract the
atomic number from the
atomic mass. For aluminum:
26.98154 -13 = 13.98154
13
13.98154
13
13 P
14 N
• Now it’s your turn. Choose any four
atoms from numbers 3 through 18 and
complete your four diagrams.