Chemical BONDING

Chemical Bond A bond results from the attraction of nuclei for electrons All atoms trying to achieve a stable octet

Two Major Types of Bonding Ionic Bonding one atom has a stronger attraction for electrons than the other. “steals” an electron from a second atom Covalent Bonding In covalent bonding the attraction for electrons is similar for two atoms. They share their electrons to obtain an octet.

IONic Bonding electrons are transferred between valence shells of atoms ionic compounds are made of ions NOT MOLECULES ionic compounds are called Salts or Crystals

[METALS ]+ [NON-METALS ]- IONic bonding Always formed between metals and non-metals [METALS ]+ [NON-METALS ]- Lost e- Gained e-

Covalent Bonding Pairs of e- are shared between non-metal atoms molecules Pairs of e- are shared between non-metal atoms

4 Steps for determining Chemical Bonds 1. Is it a Metal or Non-metal?

4 Steps for determining Chemical Bonds Determine if the bond is covalent or ionic. Covalent IONIC Non-metal + Non-metal Metal + Non-metal

4 Steps for determining Chemical Bonds Determine the number of valance electrons for each element. Can be found easily by looking at the group number on the periodic table

4 Steps for determining Chemical Bonds Draw the Lewis Structure for each element

4 Steps for determining Chemical Bonds Now you are ready to create the bond between elements. If the elements are forming a covalent bond they will be sharing electrons and have no charge

4 Steps for determining Chemical Bonds IF the elements are IONIC they will be giving or taking an electron from the outershell and will have a positive or negative charge.

Ions An ion is a charged atom Positive ion- an atom that loses one or more electrons ion a transfer Negative Ion- an atom that gains an electron from the transfer. NaF MgCl AlCl

Ionic bonding Ionic bonding involves 3 steps (3 energies) 04/10/99 Ionic bonding involves 3 steps (3 energies) loss of an electron(s) by one element gain of electron(s) by a second element attraction between positive and negative e– 1) 2) Na Cl 3) Cl– Na+ Cl– Na+

Ionic bonding ( Li + Cl) 04/10/99 Ionic bonding (stealing/transfer of electrons) can be represented in three different ways 3p+ 4n0 2e- 17p+ 18n0 8e-8e-2e 3p+ 4n0 2e-1e- 17p+ 18n0 7e- 8e- 2e- 1e- Li Cl [ Cl ]– [Li]+

Ionic bonding: Mg + O Mg + O  [Mg]2+[O]2– O Mg [ O ]2– [Mg]2+ 1e- 1e- 04/10/99 Mg + O  [Mg]2+[O]2– 12p+ 12n0 2e- 8e- 2e- 6e- 2e- 8n0 8p+ 8e- 2e- 8n0 8p+ 1e- 12p+ 12n0 2e- 8e- 1e- O Mg [ O ]2– [Mg]2+

Ionic bonding: Al + Cl Al + 3Cl [Al]3+[Cl]3– Cl Al Cl [ Cl ]3– [Al]3+ 04/10/99 Al + 3Cl [Al]3+[Cl]3– Cl Al Cl [ Cl ]3– [Al]3+ Cl

Now you try with NaCl

[Na]+ [ Cl ]- NaCl This is the finished Lewis Dot Structure How did we get here?

Always remember atoms are trying to complete their outer shell! The number of electrons the atoms needs is the total number of bonds they can make. Ex. … H? O? F? N? Cl? C? one two one three one four

Try another one: Methane CH4

Methane CH4 This is the finished Lewis dot structure How did we get here?

What did the atom of fluorine say to the atom of sodium? You complete me.