Isotopes
Lewis dot diagrams
and predicting reactions
But First, Let’s Review!!
• Name the three
subatomic particles
that an atom is made
of.

• Protons, neutrons,
electrons
But First, Let’s Review!!
• How do I calculate the
number of protons?

• It’s the same as the
atomic number!
But First, Let’s Review!!
• How do I know how
many neutrons there
are?

• Round the atomic
mass and subtract the
atomic nu...
But First, Let’s Review!!
• How do I know how
many electrons there
are?

• It’s the same as the
number of protons!
That’s ...
But First, Let’s Review!!
• Where does most of
the atoms mass come
from? AND what
subatomic particles
does it include?

• ...
But First, Let’s Review!!
• How many electrons
are on the first,
second an third shell?

• 2, 8, 8
But First, Let’s Review!!
• Who can draw a Bohr
diagram for Sulfur?
Great Job!
NOW we can learn more stuff!
Isotopes
• Isotopes are another type of atom of the
same chemical element with a different
number of neutrons.
• An isotop...
Isotopes
• Some isotopes are radioactive while most
are quite stable.
• C14 is a radioactive form of Carbon, where C13
is ...
Lewis dot Diagrams
• When predicting reactions, valence
electrons are very important!!!
• Valence electrons- electrons tha...
Lewis dot Diagrams
• Bohr Diagram:

F

• Lewis dot Diagram:

F
Lewis dot Diagrams
• This diagram allows us to focus only on the
valence electrons- which is all we really
care about when...
Lewis dot Diagrams
• One more short-cut: Rather than have to draw a
Bohr diagram first, or do the math to figure out the
n...
Predicting Reactions
• RULE 1: Everyone wants to be a noble gas!!
The noble gasses are PERFECT. They have a
full outer she...
Predicting Reactions
• Atoms are lazy (like you!) and they don’t
want to do too much work. If they only need
to lose 1,2, ...
Predicting Reactions
• If I have Beryllium and Oxygen, how many
atoms of each will I need to satisfy both
rules?
• Berylli...
Predicting Reactions

Be

O

We only need one of each! Beryllium is happy
because it lost the two outer electrons, and
wen...
Predicting Reactions: Lithium
Lithium is atomic number 3
How many protons does Lithium have?
How many Neutrons does it hav...
Predicting Reactions: Lithium
• Will lithium try to lose it’s 1 electron? Or will
it try to find 7? Which is easier?
• Who...
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Isotopes, Lewis Dot Diagrams and Predicting Reactions

  1. 1. Isotopes Lewis dot diagrams and predicting reactions
  2. 2. But First, Let’s Review!! • Name the three subatomic particles that an atom is made of. • Protons, neutrons, electrons
  3. 3. But First, Let’s Review!! • How do I calculate the number of protons? • It’s the same as the atomic number!
  4. 4. But First, Let’s Review!! • How do I know how many neutrons there are? • Round the atomic mass and subtract the atomic number!
  5. 5. But First, Let’s Review!! • How do I know how many electrons there are? • It’s the same as the number of protons! That’s how the charge of the atom stays neutral!
  6. 6. But First, Let’s Review!! • Where does most of the atoms mass come from? AND what subatomic particles does it include? • The nucleus and it consists of protons and neutrons!
  7. 7. But First, Let’s Review!! • How many electrons are on the first, second an third shell? • 2, 8, 8
  8. 8. But First, Let’s Review!! • Who can draw a Bohr diagram for Sulfur?
  9. 9. Great Job! NOW we can learn more stuff!
  10. 10. Isotopes • Isotopes are another type of atom of the same chemical element with a different number of neutrons. • An isotope of Carbon, is still carbon it just has different neutrons in the nucleus. • Having more neutrons does not affect the atomic number because the number of protons stays the same.
  11. 11. Isotopes • Some isotopes are radioactive while most are quite stable. • C14 is a radioactive form of Carbon, where C13 is a stable isotope. • C14 still has 6 protons (because the atomic number has not changed) but has 8 neutrons instead of 6.
  12. 12. Lewis dot Diagrams • When predicting reactions, valence electrons are very important!!! • Valence electrons- electrons that are on the outermost shell. • Lewis dot diagrams are similar to Bohr Diagrams but they only show the outermost shell.
  13. 13. Lewis dot Diagrams • Bohr Diagram: F • Lewis dot Diagram: F
  14. 14. Lewis dot Diagrams • This diagram allows us to focus only on the valence electrons- which is all we really care about when predicting reactions.
  15. 15. Lewis dot Diagrams • One more short-cut: Rather than have to draw a Bohr diagram first, or do the math to figure out the number of valence electrons- all you need to do is look at the number at the top of the column. • EX: Phosphorus is in group 17, so it has 7 valence electrons. • EX: Carbon is in group 14, it has 4 valence electrons • EX: Hydrogen is in group 1, it has 1 valence electron
  16. 16. Predicting Reactions • RULE 1: Everyone wants to be a noble gas!! The noble gasses are PERFECT. They have a full outer shell. All elements want to have a full outer shell. • RULE 2: No one plays unless everyone is happy. All elements reacting must get what they want or no one reacts.
  17. 17. Predicting Reactions • Atoms are lazy (like you!) and they don’t want to do too much work. If they only need to lose 1,2, or 3 electrons, they will do that rather than search for 5,6, or 7 to fill their shell. • Atoms will do the least amount of work to gain or lose electrons in order to have a full outer shell. • Remember 2 on the first shell is full! ! !
  18. 18. Predicting Reactions • If I have Beryllium and Oxygen, how many atoms of each will I need to satisfy both rules? • Beryllium has 2 valence electrons that it wants to get rid of. • Oxygen has 6 valence electrons and needs to gain 2.
  19. 19. Predicting Reactions Be O We only need one of each! Beryllium is happy because it lost the two outer electrons, and went to its inner full shell. Oxygen is happy because with Berylliums two electrons it now has a full outer shell!
  20. 20. Predicting Reactions: Lithium Lithium is atomic number 3 How many protons does Lithium have? How many Neutrons does it have? How many electrons does it have? How many valence electrons does it have? (What group is it in?) • What would a Bohr Diagram look like for Lithium? • • • • •
  21. 21. Predicting Reactions: Lithium • Will lithium try to lose it’s 1 electron? Or will it try to find 7? Which is easier? • Who is it lost likely to bond with? Who needs to find an extra electron in order to be happy? • What will the charge of it be in the end?
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