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)