Transcript Notes #2

LaVigne
Chemistry
Chapter 6/7
Notes #2
Classification of Elements
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H:
Li
Na
K
1s1
[He]2s1
[Ne]3s1
[Ar]4s1
What do elements in
the same groups have
in common with one
another?
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Be:
Mg
Ca
Sr
[He]2s2
[Ne]3s2
[Ar]4s2
[Kr]5s2
Same number of
valence electrons
(electrons in the
outermost energy level)
Classification of Elements
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Elements in the same group have similar
chemical properties because they have the
same number of valence electrons
The energy level of an element’s valence
electrons indicated the period on the periodic
table that it is found in.
Representative elements - # of valence
electrons are also related to group number
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Periodic Table
Valance Electrons
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Electrons in the outermost energy level
(highest s and p sublevels)
Ex. Mg
Ex. Br
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Columns on the periodic Table (1-8)
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Electron Dot Structures
Shows the number of valence electrons
(electrons in the outermost energy level)
of an atom
 Write the chemical symbol – put dots
around it
Element
Group
e- dot
Magnesium
2
Fluorine
7
Nitrogen
5
Carbon
4
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Classification of ElementsBlocks
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s-Blocks: Groups 1
and 2
 The alkali and
alkaline earth
metals
 Different numbers
of nonvalence eresult in different
properties
Periodic Table
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Hydrogen (an exception)
 1A, 1 ve-, but halogen
props.
 Can gain or lose one
electron
 Gaining makes it act
like a nonmetal
 Losing makes it act
like a metal
 Can be created by
electrolysis of water or
adding a metal to an
acid
Alkali metals
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Group 1 – one valence electron
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Soft and shiny metals
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Soft enough to cut with a knife
Very reactive – so they are mostly found as
compounds in nature
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Can lose a valence electron, gets a +1 charge (oxidation
state)
Violently reacts with water (it gets stored in oil so it
doesn’t react with water vapor in the air)
More reactive as you move down the column
Periodic Table
Alkaline Earth Metals
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Group 2 – 2 valence electrons
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Shiny solids, harder than alkali’s
Earth’s – didn’t melt in fire
Do not dissolve in water very well
Also very reactive
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Can lose 2 e- and can have a +2 charge (oxidation
state)
Not as reactive as alkali metals
Found as compounds most of the time
More reactive as you move down the column
Classification of ElementsBlocks
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p- block: groups 3-8
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Different numbers of
non-valence e- result in
different properties in
each column
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Group 3 – 3 v.e
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Commonly Oxide
compounds
Group 4 – 4 v.e
C = unlike other
elements in its group
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Periodic Table
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Graphite, diamond
(allotropes – same
element, different
structures, different
properties)
Carbon Chem= organic
More p-block Elements
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Group 5 – 5 V.eN- used in ammonia
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Bacteria can turn env. N
into a form plants &
animals use
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Group 6 – 6 V.eO=
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most abundant element
in Earth’s Crust
Is ozone (O3)
Other Metals = Poor
metals
Other nonmetals
Important (for living
things
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Oxygen, Nitrogen,
Sulfur, Carbon
Periodic Table
Halogens
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Group 7 – 7 valence electrons
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Very reactive gases
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Fluorine is the most reactive element
Mostly found as compounds
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Tend to gain an e- to get full outer shell
Results in a -1 charge (oxidation state)
Chorine is found in many cleaning compounds (bleach,
etc)
Halogen means “salt former”
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Tend to form compounds referred to as salts (NaCl,
MgCl2, etc)
Exception = astinine – radioactive, no known uses
Noble Gases
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Group 8 – 8 valence
electrons
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Full outer energy level of
electrons (octet rule)
Inert (non-reactive)
colorless
Exist as single atoms
Periodic Table
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Helium is the
exception to the
rule
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Only has only ssublevel e- (it only
has 2)
But is full, and
shares properties
with the noble
gases
Classification of ElementsBlocks
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d- block: Transition
Elements
 Conductors, malleable,
ductile, lustrous
 Hard with high m.p.
And b.p.
 The more unpaired
e- in d sublevel, the
higher the mp and
bp are, + are harder
 Little variation in size
and reactivities
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Can form atoms with
varying charge (multiple
oxidation states)
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Unpaired d e- can also be
lost
A change in charge
can be detected by a
color change
Classification of Elements- Blocks
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f-block: Inner transition Elements
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Lanthanides –
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(periodic table)
silvery metals with high melting points
Actinides –
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Radioactive
3 exist in nature (Th, Pa, and U) – the rest are
synthetic
All decay very quickly (except plutonium – so it is
often used in nuclear reactors)