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. – Dealing with transition metals is a bit more complex, but we still mostly deal with s and p electrons first Core electrons -those in the energy levels below.
Keeping Track of Electrons Atoms
in the same column – Have the same general outer electron configuration. – Have the same valence electrons. Electrons can easily be found by looking up the group number on the periodic table. – Group 2 - 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 electrons up until there are no open spots left
The Electron Dot diagram for Nitrogen Nitrogen
has 5 valence electrons. First we write the symbol. Then add 1 electron at a time to each side. Until they are forced to pair up.
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. 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
Electron Dots For Cations Metals
will have few valence electrons These will come off
Electron Dots For Cations Metals
will have few valence electrons These will come off Forming positive ions
Electron Configurations for Anions Nonmetals
gain electrons to attain noble gas configuration. They make negative ions. 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
electrons.
will have many valence
Electron Dots For Anions Nonmetals
will have many valence
electrons. They will gain electrons to fill outer shell.
Electron Dots For Anions Nonmetals
will have many valence electrons. They will gain electrons to fill outer shell. Forming negative ions
Stable Electron Configurations All
atoms react to achieve noble gas configuration. Noble gases have 2 s and 6 p electrons. – Again, we ignore the d electrons – 8 valence electrons . This is called the octet rule.
Stable Electron Configurations Which
elements on the periodic table do not achieve a true octet when making stable, naturally occurring ions?
H+1,
Li+1, Be+2, B+3, H-1
Ionic Bonding Anions
and cations are held together by opposite charges. – Attraction between opposite charges is called electrostatics Ionic compounds are called salts. – Salts are what is left over when an acid and base react
Ionic Bonding The
simplest ratio of the atoms in an ionic compound is called the formula unit.
Ionic
bonds are formed through the transfer of electrons.
Electrons
are transferred to achieve noble gas configuration for both atoms/ions.
Ionic Bonding
Ionic Bonding
Electronegativity applies here. The chlorine has a higher attraction to the electrons so . . .
Ionic Bonding
The electron is transferred to the chlorine
Ionic Bonding
The electron is transferred to the chlorine
Ionic Bonding
+
-
Making the atoms into ions
Ionic Bonding
+
-
Ionic Bonding
+
-
Ionic Bonding All
the electrons must be accounted for!
Ionic Bonding
Ionic Bonding
+2
Ionic Bonding
+2
Ionic Bonding
+2
-3
Ionic Bonding
+2
-3
Ionic Bonding
+2 +2
-3
Ionic Bonding
+2 +2
-3
Ionic Bonding
+2 +2
-3
Ionic Bonding
+2 +2
-3
+2
-3
Ionic Bonding
3
2
Formula Unit
Properties of Ionic Compounds They
are formed as crystalline structure. – A regular repeating arrangement of ions in the solid. – Ions are strongly bonded (electrostatic attraction) – Crystal structure is very rigid
Ionic
compounds have high melting points – because of strong forces between ions.
Crystalline structure
Do they Conduct? Conducting
electricity means charges are allowed to move. In a solid, the ions are locked in place – No charges can move Ionic solids are excellent insulators
Do they Conduct? Melting
the compounds allows the ions to move freely. When melted the ions are no longer locked in place – Separate ions can move – Moving ions can conduct electricity Molten ionic compounds conduct electricity – First get them to around 800ºC – Then the ions have freedom of movement
Do they Conduct? When
dissolved water allows the ions to separate – Separate ions can move – Moving ions can conduct electricity
Metallic Bonds How
electrons are held together in the metallic solid – Metals hold onto their valence electrons very loosely • Due to a small electronegativity
– Electrons are not held in the valance shell Think of metals as positive ions floating in a sea of electrons
