Unit 3 Periodic Properties - Lewis Structures and Ions
Name:_________________ Pd:___
Answer the following questions:
1. How do you determine the number of valence electrons for an atom?
2. How many valence electrons do each of the following atoms contain?
Potassium:
Sulfur:
Silicon:
Calcium:
Stability
 Full energy level - _______________________
 Full sublevel (s, p, d, f) - __________________
 Half-full sublevel _______________________
Electron Configuration Exceptions
- Copper
o Expect - ___________________________
o Actual - ___________________________
o Copper (all the other elements in its group) gains ________________ with a full dsublevel
- Chromium
o Expect - ___________________________
o Actual - ___________________________
o Copper (all the other elements in its group) gains ________________ with a full dsublevel
Practice 1
• What is the electron configuration for the element Gold?
Practice 2
 What electron configuration for Carbon would provide the atom with most stable configuration?
a) 1s2 2s2 2p2
b) 1s2 2s1 2p3
c) [He] 2s2 2p2
d) [He] 2s2 2p3
 In what way does this provide the atom a more stable configuration?
Lewis Electron Dot Structures
• Use Valence Electrons (_________________ ___________________).
•
There can be as many as _____ valence electrons (______ from _____ and _____ from ____)
•
Use a _____ to represent each valence electron.
•
For example: Chlorine
Name:________________________
Date:_____________________________ Pd:___________
Write the # of valence electrons and the dot diagram for each element:
1. Li
2. S
3. Ba
4. Sn
5. At 6. Si
Ion- Atom’s which either ___________ or ____________
_____________________.
- They do this to become more stable.
- They become ISOELECTRONIC:
- This is called the OCTET RULE:
Fluorine ______ an electron and becomes _______ charged
Sodium _____an electron and becomes ___charged
F + e-  F-
Na  Na+ + e-
Practice 3:
Fill in the table below for each element:
Element
Sr
I
In
Total #
Valence
Electrons
Closest Nobel gas
to become
isoelectronic with
Will this element
gain or lose
electrons?
How many
electrons will it
gain or lose?
What is the
new charge of
the element?
Is this a
cation or
anion?
Name:________________________
Date:_____________________________ Pd:___________
Po
Fr
Fill in the chart below pertaining to Cations and Anions:
Cation
Anion
Use your periodic table to help
 ______________________________ is the name given to the coulombic attraction in
chemistry
– It is the pull that an electron “feels” from the nucleus.
Name:________________________
Date:_____________________________ Pd:___________
 The closer an electron is to the nucleus, the more pull it feels.
 As effective nuclear charge increases, the electron cloud is pulled in tighter.
 (-) Electrons attracted to (+) nucleus
 3 factors that effect this
 The more protons in the nucleus, the greater the Zeff
 The more distance between the nucleus and electrons the smaller the Zeff
 ______________________________________________________
_____________________________________________________
______________________________________________________
The effective nuclear charge can be estimated from
•
•
•
Zeff = effective nuclear charge
Z = # of protons (nuclear charge)
S= shielding electrons (core electrons)
Electron Shielding
CORE electrons are closer to the nucleus and therefore have a stronger attraction to the positive
nucleus. This “shields” valence electrons from feeling as strong of a pull from the positive nucleus.
Examples:
What is the effective nuclear charge for a valance electron of oxygen?
What is the effective nuclear charge for a valance electron of fluorine?
What is the effective nuclear charge of an electron in the third energy level for the
element potassium?
What about the fourth energy level?
Cation is SMALLER than parent element because:
Anion is LARGER than parent element because:
-
Name:________________________
Date:_____________________________ Pd:___________
Lewis Dot and Periodic Trends Wrap Up Classwork:
Element
Valence Electrons
Ion with charge
Equation for formation of
ion (showing arrow and
electrons)
Ion Bigger or
smaller than
parent atom?
O
F
Be
Al
K
Br
Explain the relationship between parent atoms and their ions
- first find out how many valence electrons and then show how they will be gained or lost.
Then indicate if the parent atom or the ion will be larger and explain WHY!
1. Na
2. Ca
3. F
4. O