How do chemists design stable compounds?
I can explain what a stable compound or molecule needs to stay that
way.
NOBEL-ITY, PART II
What do we know about the
periodic table?
 As we move from left to right, what happens?
 What is a valence electron?
 What makes an element happy (stable)?
 How can you make an unstable atom stable?
 Electronegativity trends?
 Ionization Energy trends?
 What is a family?
 What is a period?
Lets start with Hydrogen
 Where is it located in the Periodic Table?
 What is the atomic number?
 What is the atomic mass?
What happens if we add a
proton?
 What happens to the valence electrons?
?
Hydrogen
P
http://commons.wikimedia.org/wiki/File:Helium-Bohr.svg
Lets Try Another…………
 Li
Be
B
C
N
O
F
Ne
 What’s happening to each element as we
move across?
http://www.bing.com/images/search?q=lithium+bohr+diagrm&FORM=IQFRBA&adlt=strict&id=3CDE39EBE5142B8E4D8329CFFF66D6E0402CBAC0&selectedIndex=4#view=detail&id=3CDE39EBE5142B8E4D83
29CFFF66D6E0402CBAC0&selectedIndex=0
What do we already know?
http://gwapchem.wikispaces.com/file/view/periodic_trends_homemade.png/213076250/763x424/periodic_trends_home-made.png
Ionization Energy
 What is it?
 How is it related to Electronegativity?
Nobel-ity, Part II
 1. Talk with your partner and answer the
following from Questions #4 and 5
 A: Families (Groups) are vertical. Which family
has the lowest, highest overall ionization energy?
 B. What is the trend within a family of elements?
 C. Period is a horizontal row. What is a trend
across periods?
 D. Indicate trends somehow…
 2. How does the number of outer electrons
relate between all noble gases?
Lets read the sidebar
 Page 184 “Electron Dot Diagrams”
 We can read it together so lets POPCORN!
 http://www.youtube.com/watch?v=ulyopnxjAZ8
http://www.marin.edu/homepages/ErikDunmi
re/CHEM105/Concept_Review/LewisDot/Lewi
sDot.html
Designing Compounds
 6f. How are the most common ions formed
for elements 1-20 related to their position on
the periodic table?
If an element is in Group 1, 2, or 3, it is easier for it to lose
electrons to become a stable positive ion.
If an element is in Group 5, 6, or 7, it is easier to gain
electrons to become a stable negative ion.
An element in group 4 can either gain or lose electrons to
become a stable ion. This are simplified rules, you will
learn more detailed rules in chemistry!
Designing Compounds
 Noble Gases have either 2 or 8 valence
electrons (a full valence shell).
 Stable ions have either 2 or 8 valence
electrons (a full valence shell) just like Noble
Gases.
Designing Compounds
 Stable compounds are electrically neutral.
 We can use this fact to predict which
compounds will be stable…
 NaCl is a stable compound. (how do you
know this from everyday experience??)
Designing Compounds
 Stable compounds are electrically neutral.
 Do you think MgCl would make a stable
compound?
Designing Compounds
 9. What is a rule for designing stable
compounds?
1. Determine the family of each element
2. Predict the charge for a stable ion of each element
3. Combine those charges to make a neutral
compound. (need the same number of positive
and negative charges)
4. Sometimes you will need more than 1 ion of a
particular element.
Designing Compounds
 9. Which of the following formulas is correct?
 NaCl2
 BaF
 KO
 Li2F
 Mg2S
 Al2O3
Designing Compounds
 How does the organization of the periodic
table help you quickly predict the correct
formulas of compounds?
Each family of elements on the periodic table is associated
with losing or gaining a certain number of electrons to
obtain a noble gas configuration. If you number each
column with the most common ion formed, then you can
use those numbers to determine the correct formula for
many binary compounds.