Transcript Chapter 7 PPT

Chapter 7
IONIC AND METALLIC BONDING
Objectives
 You WILL be able to…
 Determine number of valence electrons in an atom of a
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representative element
Explain how the octet rule applies o atoms of metallic
and nonmetallic elements
Describe how cations form
Explain how anions form
Explain the electrical charge of an ionic compound
Describe 3 properties of ionic compounds
Model the valence electrons of metal atoms
Describe the arrangement of atoms in metal
Explain the importance of alloys
Ions
 Valence Electrons – Electrons in the highest
occupied energy level of an element’s atoms
 The number of valence electrons determines an
element’s properties
 Group number indicates the number of valence e-
 The Octet Rule- the achievement of 8 electrons in the
highest energy level of an atom
 Done by losing, gaining, or sharing valence electrons
Formation of Cations
 Cations form when atoms lose valence electrons
 Metals usually do this because they only have a few
valence electrons and they have low ionization energies
 The loss of valence electrons makes the cation more
stable than the atom because there is an complete octet
in the valence shell
For example:
Na = 1s22s22p63s1 and Na + = 1s22s22p6
Monatomic cations are named using the name of the
element (ie sodium ion, magnesium ion)
 Some metals that easily give up valence electrons are…
 Alkali metals (+1 charge)
 Alkali Earth Metals (+2 charge)
 Aluminum (+3 charge)
 Heavier group IV and V elements (Sn +2 or +4; Pb +2 or
+4; Bi +3)
 Most transition and inner transition elements (Ag+1, Zn
+2, Cr +3; most rare earth metals +3)
 Some transition metals have cations with varying charge
depending on what they are bonded with (ie Fe +3 and
Fe+2)
Formation of Anions
 Anions form when atoms gain valence electrons
 The gain of valence electrons makes the anion more
stable than the atom because there is now a complete
octet in the valence shell
 For example:
Cl = 1s22s22p63s23p5
and Cl - =1s22s22p63s23p6
Anions are named using the root of the element’s
name plus the ending –ide (ie. bromide, chloride)
 Some nonmetals easily acquire electrons…
 Halogens (-1 charge)
 Chalcogens (-2 charge)
 Nitrogen (-3 charge)
 Polyatomic Ions are comprised of two or more atoms
covalently bonded that can be considered as acting
as a single particle
Ionic Bonds and Ionic Compounds
 Ionic bonds are formed when the charges on positive
ions balance the charges on the negative ions
through electrostatic attraction
 Formula units are the lowest whole number ratio of
ions in an ionic compound.
 Chemical formulas are shorthand ways of showing
the amounts and the types of elements in the
smallest representative unit
Example: NaCl, CaBr2, AlI3 (salts)
Electron Dot Formulas-Open and closed circles or x’s
 Ionic attractions are so strong that almost all ionic
compounds are solid with unique crystalline
structures
 The strength of the bonds also leads to high melting
points and boiling points
 Ionic bonds almost always occur between metals and
nonmetals
 Ionic compounds are also good conductors of
electricity if dissolved in water or molten
 Ionic compounds are electrically neutral, therefore
the number of positive charges is the same as the
number of negative charges.
Colors of Ionic Compounds
 Transition metal ions having partially filled d
orbitals usually have a color.
 For example…
 NiSO4
 FeCl3
 CuSO4
 Metal cations that have no d electrons or completely
filled d orbitals are usually not colored.
 NaCl
MgSO4
 CaCl2
ZnCl2
Metals in Bonding
 Metals have loosely held valence electrons
 When metal atoms exist in the solid form of a metal
all the nuclei share all the valence electrons of all the
atoms in the sample
“Electron Sea”
 The “sea of electrons” explains physical properties
such as conductivity, malleability, and ductility
 Metals are arranged in compact and orderly patterns
Alloys
 Mixtures of two or more elements where at least one
is a metal
 Steel, brass (Cu and Zn), bronze
 Mixing alloys will result in a metal with superior
properties than those of the component materials
Them’s
22’s son!!!