bonding ionic bonding & metallic bonding keeping track of electrons l the electrons responsible...
TRANSCRIPT
Bonding
Ionic Bonding
&
Metallic Bonding
Keeping Track of Electrons The electrons responsible for the
chemical properties of atoms are those in the outer energy level.
Valence electrons - The s and p electrons in the outer energy level.
Core (kernel)electrons -those in the energy levels below.
Keeping Track of Electrons Atoms in the same column Have the same outer electron
configuration. Have the same valence electrons. Easily found by looking up the group
number on the periodic table. Group 2A - Be, Mg, Ca, etc.- 2 valence electrons
Electron Dot diagrams A way of keeping track of
valence electrons. How to write them Write the symbol. Put one dot for each
valence electron Don’t pair up until they
have to
X
The Electron Dot diagram for Nitrogen
Nitrogen has 5 valence electrons.
First we write the symbol.
NThen add 1 electron at a time to each side.
Write the electron dot diagram for
Na Mg C O F Ne He
Electron Configurations for Cations
Metals lose electrons to attain noble gas configuration.
They make positive ions. (Cations) If we look at electron configuration it
makes sense. Na 1s22s22p63s1 - 1 valence electron Na+ 1s22s22p6 -noble gas configuration
Electron Dots For Cations Metals will have few valence electrons
Ca
Electron Dots For Cations Metals will have few valence electrons These will come off
Ca
Electron Dots For Cations Metals will have few valence electrons These will come off Forming positive ions
Ca+2
Electron Configurations for Anions
Nonmetals gain electrons to attain noble gas configuration.
They make negative ions. (Anions) If we look at electron configuration it
makes sense. S 1s22s22p63s23p4 - 6 valence electrons S-2 1s22s22p63s23p6 -noble gas
configuration.
Electron Dots For Anions Nonmetals will have many
valence .electrons. They will gain electrons to fill outer shell.
P P-3
Stable Electron Configurations All atoms react to achieve noble gas
configuration. Noble gases have 2 s and 6 p electrons. 8 valence electrons . Also called the octet rule.
Ar
Ionic Bonding Anions and cations are held together by
opposite charges. (metal and non-metal)
Ionic compounds are called salts. Simplest ratio is called the formula unit. The bond is formed through the transfer
of electrons. Electrons are transferred to achieve
noble gas configuration. Atoms are generally far apart on table EN difference of 1.7 or greater.
Ionic Bonding
Na Cl
Ionic Bonding
Na+ Cl-
Ionic Bonding All the electrons must be accounted for!
Ca P
Ionic Bonding
Ca P
Ionic Bonding
Ca+2 P
Ionic Bonding
Ca+2 P
Ca
Ionic Bonding
Ca+2 P-3
Ca
Ionic Bonding
Ca+2 P-3
Ca P
Ionic Bonding
Ca+2 P-3
Ca+2 P
Ionic Bonding
Ca+2 P-3
Ca+2 P
Ca
Ionic Bonding
Ca+2 P-3
Ca+2 P
Ca
Ionic Bonding
Ca+2 P-3
Ca+2P
-3
Ca+2
Ionic Bonding
Ca3P2
Formula Unit
Writing Ionic FormulasCriss Cross Method
Ca +2 P -323
Ca3 P2
Ca3P2
Properties of Ionic Compounds Crystalline structure. A regular repeating arrangement of ions
in the solid. Ions are strongly bonded. Structure is rigid. High melting points- because of strong
forces between ions.
Crystalline structure
Ionic solids are brittle
+ - + -+- +-
+ - + -+- +-
Ionic solids are brittle
+ - + -
+- +-+ - + -
+- +-
Strong Repulsion breaks crystal apart.
Reactions of Metals Lose electrons Become positive ions (Cations) Have smaller radii Acquire the noble gas configuration
Reactions of Non-Metals Gain electrons Become negative ions (Anions) Have larger radii Acquire the noble gas configuration
Do they Conduct? Conducting electricity is allowing charges to move. Solids:
– the ions are locked in place.
– (NaCls) so NO conductivity.
– Ionic solids are insulators. When melted,(NaCll ) the ions can move around. So
YES conductivity.– Ionic solids have high melting points. (800ºC) – Melted means molten
Dissolved in water(NaClaq) YES conductivity.
Metallic Bonds Metal bonded to more metal. (Ag, Au,
Sn, etc. all have metallic bonds.) How atoms are held together in the
metallic solid. Metals hold onto their valence electrons
very weakly. Think of them as positive ions floating in
a sea of electrons.
Sea of Electrons
+ + + ++ + + +
+ + + +
Electrons are free to move through the solid.
Metals conduct electricity and heat.
Metals are Malleable Hammered into shape (bend). Ductile - drawn into wires.
Malleable
+ + + ++ + + +
+ + + +
Malleable
+ + + +
+ + + ++ + + +
Electrons allow atoms to slide by.
Ductile
+ + + +
+ + + ++ + + +
Electrons can be drawn into a thin wire.
Energy Changes in Bond Formation Chemical Bonds are forces that hold
atoms together. Energy is required to overcome these
attractive forces and separate the atoms in a compound.
Breaking a bond Endothermic – Energy on left side of rxn AB + 100J A + B
Making a bond Exothermic– Energy on right side of rxn A + B AB + 100J
Energy and Stability The greater the amount of energy
released in forming the bond the greater its stability.
B + C BC + 100 joules K + L KL + 400 joules
(more stable)