Valence electrons

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1
8
Valence electrons
2
3
4
5
6
7
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Nonmetals
Metals
Metalloids

• Reflective (shiny)

• Dull

• Good conductors of heat and electricity

• Poor conductors of heat and electricity

• Usually solid

• Usually gases

• Malleable can be beaten or rolled into thin
  sheets

• If solid, are brittle

• Ductile can be drawn into wires

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Named Families
Just like with people, elements are grouped into
families by similarities in their properties.
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Alkali metals
Noble gases
Halogens
Alkaline earth metals
Transition Metals
Inner Transition Metals
(Rare Earths)
Lanthanides
Actinides
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Noble gas configuration a very stable, low
energy electron configuration because the
outermost energy level is completely filled
He 1s2
Ne He 2s2 2p6
Ar Ne 3s2 3p6
Ex

• Elements that have partially filled outer
  orbitals will gain or lose electrons in order to
  achieve the stability of a noble gas
  configuration.

• When an atom gains or loses electrons, it is no
  longer electrically neutral and is called an ion.

Cation an ion with a positive charge (atom has
lost electrons) Anion an ion with a negative
charge (atom has gained electrons)
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Ion
Atom
Oxidation number
Subtract 1 e- ? 1 charge
Li1 He 2s0
Li He 2s1
Be He 2s2
Be2 He 2s0
2 e- ? 2 charge
B He 2s2 2p1
B3 He 2s0 2p0
3 e- ? 3 charge
C He 2s2 2p2
Carbon can either lose four electrons or gain
four electrons ? doesnt form ions readily
N He 2s2 2p3
N-3 1s2 2s2 2p6
Add 3e- ? -3 charge
O He 2s2 2p4
O-2 1s2 2s2 2p6
2 e- ? -2 charge
F He 2s2 2p5
F-1 1s2 2s2 2p6
1 e- ? -1 charge
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Oxidation Numbers of Representative Elements
1
4
2
3
-3
-2
-1
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Diamagnetism and Paramagnetism
Atoms or ions with any unpaired electrons are
paramagnetic and will respond to a magnetic field

• Fe2 is paramagnetic because it has unpaired
  electrons

Atoms or ions in which ALL of the electrons are
paired are diamagnetic and will not respond to a
magnetic field
Zn is diamagnetic because there are NO unpaired
electrons
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Periodicity Atomic Trends

• There are a number of atomic characteristics that
  either increase or decrease along the periodic
  table.

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• Atomic Radius
• As you go down a group, the atomic radius
  increases due to increased shielding.

Atomic radius decreases as you go left to right
along a period due to increasing effective
nuclear charge.
s-block
p-block
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Shielding Effect The inner electron shells
insulate the valence electrons from some of the
electrical attraction with the positive charge of
the nucleus.
nucleus
core electrons
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Shielding Effect The inner electron shells
insulate the valence electrons from some of the
electrical attraction with the positive charge of
the nucleus.
nucleus
core electrons
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Increasing Effective Nuclear Charge Electrons
in the outermost energy levels do not effectively
screen each other from an increasingly positive
nucleus.
nucleus
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The size of an atom is mostly determined by the
number of electrons around the nucleus.
Thus size (radius) ? as the negative charge ?
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• Ionization Energy the amount of energy that is
  required to remove an electron.
• If an atom will easily lose an electron (like the
  alkali metals), the ionization energy will be
  low.
• If it will not lose electrons easily (noble
  gases, halogens), the ionization energy will be
  high.

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• Electronegativity Ability of an atom to attract
  electrons when in a molecule.

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• Electronegativity increases going left to right,
  and decreases going down.

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Periodicity Atomic Trends

• There are a number of atomic characteristics that
  either increase or decrease along the periodic
  table.

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Chapter 7 Elements with Color
red
Metals
Nonmetals
white
Halogens
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Allotropes different structural forms of the
same element
Allotropes of Carbon
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There are three types of bonding in chemistry.
Covalent
(nonmetal nonmetal)
(metal nonmetal)
Metallic
(metal metal)
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When two metals combine together, they form
METALLIC bonds. The low ionization energy of a
metal atom causes the electrons to only be
loosely held by the nuclei. The valence
electrons are delocalized and are distributed in
an electron sea around the positively charged
metal centers.

• Properties It is because the electrons are not
  localized around a particular nucleus that metals
  are shiny, malleable, ductile and good conductors
  of heat and electricity.

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Alloys mixtures of two or more metals
The three types of alloys
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When nonmetals combine together, they SHARE
electrons to form COVALENT bonds.
Example Combine 2 hydrogens and 1 oxygen to form
H2O, a compound.
The electrons between the hydrogen and the oxygen
are shared. They form a COVALENT bond.
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When nonmetals combine together, they SHARE
electrons to form COVALENT bonds.
H
O
H
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When two metals combine together, they form
METALLIC bonds. Unlike nonmetals, the electrons
in metals are distributed throughout the metal.
This is often called the electron sea.
Electrons are swimming around the positive nuclei
in an electron sea.
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When nonmetals AND metals combine together, they
TRANSFER electrons to form IONIC bonds.
-1
1
Na

Sodium has LOST one of its electrons in the
transferit now has a 1 charge.
Chlorine has GAINED one extra electron in the
transferit now has a -1 charge.