Key Terms: Octet RuleIon CationAnion

What is the difference between an atom and an ion? How can an atom become an ion? Why do chemists call table salt sodium chloride? Why do chemists write the formula for sodium chloride as NaCl?

 Some elements are highly reactive, others are not. Which are the most reactive?  Reactivity depends on the electron configuration.  They want to lose or gain electrons to be like the noble gases

 Write out potassium’s electron configuration ◦ 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 ◦ What does it want to do to become more like a noble gas? ◦ The HIGHEST energy level is “4”  So the “4’s” want to have ___________ electrons.  Write out Argon’s electron configuration

 The Periodic Table tells us how many valence electrons each element has.  The electron configurations tell us this pattern exists. [Mg] = [Ne] 3s 2 tells us two valence e - ’s [P] = [Ne] 3s 2 3p 3 tells us five valence e - ’s

 Remember in naming, we cross the charges to form a neutral compound.  But, to make Na or K stable, they want to GIVE AWAY one electron!!  Sodium still has 11 protons but now 10 e - ’s  This gives sodium a ________ charge.  Think about Chlorine now.

 Sodium loses one electron and then forms a _________ charge  Chlorine gains one electron and then forms a _________ charge.  We call ions with a positive charge _________ and ions with a negative charge _________.

Na  Na + + e - Cation 11 protons and now only 10 electrons Cl + e -  Cl - Anion 17 protons but now 18 electrons

 Since the number of protons and, more importantly, the number of neutrons are the same, the nucleus is unchanged. It is still Na. ◦ The only thing that has changed is the number of electrons.  They WANT to obtain ________ valence electrons sooooo they are MORE stable now!

 Some stable ions do not have noble-gas configurations  The transition metals are often stable without complete octets.  For example, Cu can give up one electrons forming a Cu + cation. It can ALSO give up two electrons, forming a Cu 2+ cation. Both are stable even without the octet configuration.

 Just because these atoms have a noble gas configuration DOES NOT mean they are more noble gases!!  What number determines the identity of the element?  The number of ______________ changes the charge NOT the identity!!

 The ions have a different set of ___________ and ___________ properties.  Sodium metal reacts violently with Chlorine gas to produce NaCl, table salt.  In water, Na + and Cl - are in solution but NOT VIOLENTLY reacting as observed between the two parent atoms.

 Atoms of metals and nonmetal elements form ions differently.  Most all metals form _____________ ions.  Most all nonmetals form _____________ ions.  Why??? ◦ Hint: Think about their e - config and the octet rule!