Chemical Bonds
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Transcript Chemical Bonds
Chemical Bonds
Chapter 6
Chemical Bonding
Combining of elements to form
new substances
1.
1st energy level holds 2 electrons
2nd and 3rd energy levels hold 8
electrons
Valence electrons = electrons found in
the outermost energy level
2.
Electron Configuration
Refers to the arrangement of the
valence (outer) electrons in an atom.
The group number usually tells us how
many valence electrons are present in
an atom
Example: magnesium (group IIA)
Electron-Dot diagrams:
A shorthand method to show valence
electrons.
When the outermost energy level is
complete, or full, the atom is
considered happy or satisfied. It is more
stable.
“Happy” atoms
The inert or noble
gases all have a
complete outer
shell. Group VIIIA
They are unreactive
for the most part.
Very stable
Bonding that involves a transfer of
electrons from one atom to another :
Happy IONS
Anions and Cations
Anion
Cation
An ion with a
negative charge
Negative ions have
GAINED electrons
Usually non-metals.
Right side of
periodic table
An ion with a
positive charge
Positive ions have
LOST electrons
Usually metals. Left
side of periodic table
What happens when atoms
lose electrons?
Ionization
The process of removing electrons and
forming ions
Ionization energy = the energy needed
to remove an electron
Different amounts of energy needed for
different elements and different
electrons of the same element.
Low and High Ionization
Energies
High ionization
LOW Ionization
energy
Energy
Many valence
Very few valence
electrons :
electrons :
Lose electrons easily Gain electrons easily
Crystal Lattice
Ions in an ionic compound are arranged
in a specific way. A regular repeating
pattern.
Very stable; High Melting points
Properties of Ionic Compounds
Usually very high melting points
Good conductors of electricity when
dissolved in water
Ionic crystals often shatter when struck.
Bonding in which electrons are
shared.
each atom will still attempt to fill its
outermost energy level
The positively charge nucleus of each
atom simultaneously attracts the
negatively charged electrons being
shared.
Covalent Bonds between more
than two atoms:
Multiple Covalent Bonds
Elements that
exist in nature as
two identical
atoms covalently
bonded to each
other (know these
seven!!!)
Equal sharing.
Molecules
The
smallest piece of a covalently
bonded substance
Very low melting points
Only a small amount of energy is
needed to separate molecules from
each other.
examples: (on white board)
Unequal sharing of electrons
In general, elements on the right tend
to have a greater attraction for
electrons.
Because of this, they “want” the
electrons more. They are “stronger” in
the electron tug-of-war.
Polar covalent bonds
Occurs when an atom has a greater
attraction for the shared electrons than
the other atom involved in the bond
Results in partial positive and partial
negative charges (+ and -)
What determines if a compound is
polar or non-polar?
1)
2)
o
The types of atoms
The shape of the molecule
Example:
Naming ionic compounds
Binary compounds:
Only consists of two elements.
The name of the cation followed by the
name of the anion.
Example: sodium chloride (NaCl)
Not sodium chlorine
See page 171
Some metal ions have more
than one charge.
Examples on page 172
A Roman numeral is placed after the
name of the metal to identify the
charge.
Polyatomic ions
A
covalently bonded group of
atoms that act like a single ion
with a net charge.
P. 173
Naming molecular compounds
Often will use Greek prefixes.(figure 20)
Examples:
SO3
CO2
P4S10
Metallic Bonds
A special type of covalent bond where
the nuclei of metal atoms are
surrounded by a “sea’ of electrons
The mobility of the electrons in a metal
lattice explains some of the properties
of metals
Alloys
A solid solution of two or more metals.
Common alloys
Bronze
Brass
Steel
Stainless steel
Gold jewelery
Copper and tin
Copper and zinc
Iron and carbon
Iron and
chromium
Gold, silver,
nickel, copper,
and zinc
Assignment:
Page
187
1-10,12,15,25
Page 189 (1-7)