Catalyst – March Uno, 2010 Monday Mystery Element! 1. A “p-block” element 2. Name is Latin for “violet” 3. When bent, makes a shrieking noise

Catalyst – March Uno, 2010 Monday Mystery Element! 1. A “p-block” element 2. Name is Latin for “violet” 3. When bent, makes a shrieking noise INDIUM!

Today’s Agenda  Catalyst  Lewis Dot Structures  Stable Ions  Octet Rule  Work Time…Oooh Oooh!  Exit Question

Today’s Objectives  SWBAT draw Lewis Dot Structures for atoms and ions.  SWBAT determine the charge on an ion.  SWBAT use the octet rule to predict the number of electrons in a stable ion.

Valence Electrons Review  Electrons in the outermost level or shell of the atom that determine the chemical reactivity of an element  Outer s and p electrons  These electrons are involved in bonding

Valence Electrons  Valence electrons are the electrons in the outside energy level NUCLEUS ALL TOGETHER, SODIUM HAS 11 ELECTRONS. SODIUM HAS 1 VALENCE ELECTRON P=11 N=12

What is a compound? Key Point #1: A compound results from interaction between valence electrons of different atoms.

Chemical Bond Spotlight: NaCl (table salt) 2 different elements:  Sodium (Na)  Chlorine (Cl) 1 compound:  Sodium chloride (NaCl) NaCl NaCl

Chemical Bond Spotlight: NaCl (table salt) Let’s see a video!

Lewis Dot Structures Key Point #2: Lewis Dot Structures only show the number of valence electrons in an atom.  Valence electrons are the only electrons involved in bonding  Valence electrons are the most important electrons

Drawing Lewis Dot Structures 1. Write element symbol. 2. Determine number of valence electrons. 3. Place single dot on right side and add single dots counterclockwise. EXAMPLES COMING UP…

Count ve-…then draw LDS 1. Boron 2. Oxygen 3. Lithium

LDS Example 1: Sodium (Na) 1. Write element symbol. 2. Determine number of valence electrons. 3. Place single dot on right side and add single dots counterclockwise.

LDS Example 2: Neon (Ne) 1. Write element symbol. 2. Determine number of valence electrons. 3. Place single dot on right side and add single dots counterclockwise.

Lewis Dot Sructures What do the Lewis Dot Structures have in common?!?!?

I have a few QUESTIONS… 1. What kind of charge does an electron have? (-1) 2. What kind of charge does an entire atom have? Neutral (as many positives as negatives) So….if an atom gains an electron what kind of charge will it have? What about if an atom loses an electron???

First thing you need to know about ionic bonds….  Key Point #3: An ion is an element that has gained or lost an electron. Cation = positive ion (+) Anion = negative ion (-) + -

Types of ions  Cation – a positive ion (+)  “t” looks like (+)  Anion – a negative ion (-)  “n” or onion for negative

Formation of Negative Ions (ANIONS)  Again, imagine that electrons are pieces of poop  Is poop is flying into your yard (an atom’s energy levels) a positive or negative thing?  So…if poop lands in your yard, are you more positive or more negative? So…NEGATIVE ions are formed when an atom GAINS one or more electrons! -

Formation of Positive Ions (CATIONS)  Imagine that electrons are pieces of poop  Is poop in your yard (an atom’s energy levels) a positive or negative thing?  So…if you get rid of the poop in your yard, are you more positive or more negative? + So…POSITIVE ions are formed when an atom LOSES one or more electrons!

Practice Questions 1. If an atom gains an electron it will have a ___________ charge. 2. If an atom loses an electron it will have a ___________ charge. 3. If chlorine gains 3 electrons it will have a _______ charge. NEGATIVE POSITIVE 3-

Ions! Cl loses 4 Electrons What is the stable ion?

Ions! Cobalt gains 2 electrons What is the stable ion?

Ions! Si 3- What happened… gain or lose… how many?

Ions Si 3- Silicon gains 3 electrons How many total electrons does Si have now?

Practice Problems – Write all down!  Write down the stable ion that will form for the following: 1. Sr gains 5 electrons 2. Phosphorous loses 1 electron  Then, answer how many electrons TOTAL will they have now?

Practice Problems – Write all down! How many TOTAL electrons do the following ions have? 1. Cl Li Xe O Zn 5-

Octet Rule  What is different about the valence shells of the elements on the Left and those on the Right?  The noble gases have full valence shells, the other atoms do not… Octet Rule – Elements are most stable when they have the electron configuration of a noble gas (Key Point next…)

Key Point #4: The octet rule says that atoms are most stable when they have 8 valence electrons. 1. Atoms can gain or lose electrons to become stable (happy) 2. Atoms with 4 or more valence electrons will GAIN electrons to become stable (happy) 3. Atoms with 3 or less valence electrons will LOSE electrons to be stable (happy) Octet Rule

Octet Rule - Examples  How many electrons will the following atoms gain or lose to become stable (happy)? How many TOTAL electrons will the atom then have? What is the STABLE ION? 1. F 2. O 3. N 4. H

Try the following on your own  How many electrons will the following atoms gain or lose to become stable (happy)? How many TOTAL electrons will the atom then have? What is the STABLE ION? 1. P 2. Kr 3. Ca 4. I 5. K

Worksheet for Class or HW Half Shee – eet! Take care of your bidness and complete it tonight!

Exit Question 1. Anion = _______ charge, Cation = _______ charge 2. What is the STABLE ION that will form for the following elements? Write down the ion and how many electrons the atom will have TOTAL.  Te  Li 4. Draw the LDS for the following elements:  Sulfur  Magnesium