Ms. Samayoa Birmingham Community Charter High School Chemistry Simple Ions Ms. Samayoa Birmingham Community Charter High School Chemistry

Learning Objective Students will learn how to predict the type of ion that a given element forms from its position on the periodic table

Simple Ions How much an element reacts depends on its valence electron configuration Ask students what reactivity property do noble gases have

The noble gases show almost no chemical reactivity Why? Simple Ions The noble gases show almost no chemical reactivity Why? Because they have a FULL valence shell of electrons! Reactions occur when atoms lose or gain electrons Because noble gases don’t lose or gain electrons there is no chemical reactivity

Simple Ions: The Octet Rule As we’ve learned before, atoms like to be stable Feel most stable when electron shells are full Electron shells become full when they have eight valence electrons This is called the OCTET RULE, which says that atoms like to have full valence shells of eight electrons Ask student to state what octet rule means

Simple Ions: The Octet Rule How many valence electrons do noble gases have? 8

Check for Understanding Explain why the noble gases tend not to react using the following vocabulary words: valence electrons and octet rule Sentence starter: Noble gases don’t tend to react because….

Simple Ions: The Octet Rule Atomsreactsothattheycanacheivethesameelectron configurationsasthenoblegases Atoms react so that they can achieve the same electron configurations as the noble gases

Write the electron configuration of POTASSIUM. PRACTICE Write the electron configuration of POTASSIUM.

Simple Ions 1s22s22p63s23p64s1 Example: Potassium (K) How many valence electrons does potassium have to lose to have an electron configuration of a noble gas? Which noble gas? Potassium wants to lose ONE valence electron to achieve the same valence electron configuration as ARGON  1s22s22p63s23p6

Simple Ions K  K+ + e After giving up one electron… Potassium still has 19 protons But only 18 electrons +19-18 = +1 Because the numbers are not the same, there is an overall electrical charge = ION K  K+ + e

Ions that have a positive charge are known as CATIONS Elements lose electrons to form cations

Finish this sentence Since potassium lost an electron, it has a ________ charge and is classified as ___________

Write the electron configuration for chlorine PRACTICE Write the electron configuration for chlorine

PRACTICE Example: Chlorine (Cl) 1s22s22p63s23p5 How many valence electrons does chlorine have to gain to have an electron configuration of a noble gas? Which noble gas? Chlorine wants to gain ONE valence electron to achieve the same valence electron configuration as Ar  1s22s22p63s23p6

Simple Ions After gaining one electron… Chlorine still has 17 protons But only 18 electrons +17-18 = -1 Because the numbers are not the same, there is an overall electrical charge = ION Cl + e  Cl-

Ions that have a negative charge are known as anions Elements GAIN electrons to form ANIONS

Finish this sentence Since chlorine gained an electron, it has a ________ charge and is classified as ___________.

Think About it… You will be given 2 minutes to find a question to the answer given. Partner A: The answer is cation. What is the question? Partner B: The answer is anion. What is the question?

Think About It… Now share with your partner: Partner A: Write down the question that your Partner B came up with in your notes and explain why anion is the answer Partner B: Write down the question that your Partner A came up with in your notes and explain why cation is the answer

Think About It… Partner A: Give an example of an element that LOSES electrons to form an ion with a POSITIVE CHARGE Partner B: Give an example of an element that GAINS electrons to form an ion with a NEGATIVE CHARGE

Exceptions Many stable ions have noble-gas configurations However some stable ions do not have noble-gas configurations Transition metals often form ions WITHOUT complete octets ALL TRANSITION METALS FORM CATIONS Notice that mostly transition metals can form several stable ions that have different charges Example copper Can give up one electron or can give up two and both are stable even though they do not have noble gas configurations

COMMON MISCONCEPTIONS “An atom and its ion have the same chemical properties.” WRONG!!!!!!!! e.g. Sodium ion vs Sodium Explain that sodium is extremely reactive Chlorine is also reactive When reacting together very violent Although made from two dangerous elements, something you can eat because they are cation and anions

COMMON MISCONCEPTIONS When an atom loses/gains electrons to form an ion, it achieves an electron configuration IDENTICAL to a noble gas That does not mean it becomes a noble gas! Na vs Ne Sodium still has ___ protons and Neon has ____ protons