8th grade Read p.51-53 Do questions 1-2, on page 51, Do definitions p. 51 and Do question 3 a and b p. 53
8th (please ask students what chapter we are on so everyone will be on the same page)
History: Flashcards for definitions and identify for chapter 5.2 and 5.3, when done outline for chapter 5.4 and flashcards for 5.4.
Whatever is not done is to be done as HWK.
Valence Electrons
Where are Electrons
located?
In the Electron Cloud
How many Levels are in
the Electron Cloud?
Three
How many Electrons fit
st
nd
rd
in the 1 /2 /3 Energy
Levels?
1st Energy Level = 2 e–
2ndEnergy Level = 8 e–
3rdEnergy Level = 8 e–
Valence Electrons
These are the electrons on
the atom’s OUTERMOST or
LAST Energy Level/shell
1. What element is pictured?
2. How many protons?
3. How many electrons?
+ +
+
4. How many neutrons?
5. What is the atomic number?
6. What is the atomic mass?
7. How many valence electrons?
+
+ + +
+
+
+ + +
+
+
+
+
+
+ +
+
+
+
+
A.
+
+
B.
+ + +
+
+ +
+
C.
Valence Electrons
Valence Electrons are used
to determine an element’s
chemical reactivity (how easily it
will react or combine or bond with other
elements)
Valence Electrons
ALL atoms want to have a
FULL outermost shell
Atoms with a full outermost
shell are the MOST stable, so
they have a very low
chemical reactivity.
The Noble Gases Group 18 all have a full outer
shell
Valence Electrons
Atoms will gain or lose
electrons to get a full outer
shell.
It is a lot easier to lose or gain
only 1 electron, so those
elements with only 1 valence
electron have a very high
chemical reactivity.
Valence Electrons
Elements in group 1 only have 1 valence
electron, so they must lose 1 electron to
have a full outer shell. This makes all
elements in group 1 highly reactive.
Elements in group 17 have 7 valence
electron, so they must gain 1 electron to
have a full outer shell. This makes all
elements in group 17 highly reactive.
Valence Electrons
All other elements with 2, 3, 4, 5, or 6
valence electrons have a moderate
chemical reactivity.
It is easier to gain/lose 2 electrons than
to lose 3 electrons, so elements with 2
valence electrons are more reactive than
those that must gain/lose 3 electrons.