Chapter 1Chapter 1Activity 7:Activity 7:
How Electrons How Electrons Determine Chemical Determine Chemical
BehaviorBehavior
Bohr Model—shows the electrons in various energy levels
How many electrons can fit into each energy level??????
Max # e- = 2n2 where n= energy level
Ex. If n=1 (1st energy level), then 2(1)2=Ex. If n=2 (2nd energy level), then 2(2)2=Ex. If n=3 (3rd energy level), then 2(3)2=
Valence ElectronsValence ElectronsValence electrons
◦Electrons in the outermost energy level of an atom
Valence ElectronsValence ElectronsThe Group Number tells us the # of valence electrons.
Valence e-
increases across a period
Valence e- stays
the same
down a group
Valence ElectronsValence ElectronsHow many valence electrons does
◦a Fluorine atom have?◦a Magnesium atom have?◦an element in the noble gas family have?◦
Things You Need to Now KnowThings You Need to Now Know
On the periodic table:
◦The COLUMN or GROUP or FAMILY equals the # of valence electrons (for columns 1,2, 13-18)
◦The ROW or PERIOD equals the energy level
Bohr ModelsBohr Models
Rutherford focused on describing the nucleus
Bohr focused on describing the location of the electrons
Bohr model (planetary model): -shows electrons moving in orbits (energy levels) around the positive nucleus of the atom.
Bohr model for HydrogenBohr model for Hydrogen
1H
1
Hydrogen is in period 1 = 1st energy level
Hydrogen is the first box in period 1 = 1 electron
Energy level 1
# of Electrons in that Energy level
Bohr model for LithiumBohr model for Lithium
3Li
2 1
Lithium is in period 2 = 2nd energy level
Lithium is the first box in period 2 = 1 electron
Energy level 1
# of Electrons in 1st Energy level
Energy level 2
# of Electrons in 2nd Energy level
Using What You Now KnowUsing What You Now KnowDuet Rule: In forming compounds,
atoms tend to gain or lose electrons in order to have two electrons in their first energy level.
Octet Rule: In forming compounds, atoms tend to gain or lose electrons in order to have eight electrons in their outer energy level.
StabilityStability
9F
2 7
Atoms will lose or gain electrons to have a filled outer energy level (duet rule or octet rule).
This fluorine atom has only 7 valence electrons
The octet rule isn’t satisfied
Stability Stability A fluorine atom will try and gain an
electron (7e- + 1e- = 8e-).
With 8e-s, it is now an ANION (-1) with 8 valence electrons
The anion now obeysthe octet rule.
-1
9F
2 8
-1
StabilityStability
11Na
2 8 1
This sodium atom has 1 valence electron.
The octet rule isn’t satisfied.
StabilityStability
11Na
2 8
If the sodium atom loses it’s valence electron, it will now have 8 valence electrons.
The octet rule is satisfied.
+1
Why Atoms ReactWhy Atoms ReactSome atoms want to lose valence electrons more
than others -nonmetals want to keep their valence electrons
-metals want to lose their valence electrons