Ions & Lewis Dot Structures Lesson 3.2 Ions

Lesson 3.2 Learning Goals SWBAT define the terms ion, cation, anion SWBAT draw Lewis Dot Structures, in order to represent the valence electrons elements, compounds, and ions.

Ions Ions are: Atoms with overall charge that is not zero/ neutral Ions can be either positively or negatively charged atoms. Created when atoms gain or lose electrons Written with a superscript designating charge: Ex: Mg2+, Cl-, Na+, O33- We have discussed atoms with a “charge” and you all know how to calculate the number of electrons according to the charge. Because we can only lose or gain ELECTRONS and ION is an atom that has gained or lost an electron

Positive Ions: Cations Cations are positive (+) ions Created when an atom loses / gives away an electron Have more protons than electrons

Whole-Class Practice: Cations Ca2+ Calcium (Ca) has atomic number 20. # protons in Ca? _______ # electrons in Ca?______ Overall charge of Ca? _______ A Ca2+ cation is formed when Ca loses two electrons. # protons in Ca2+ ?_______ # electrons in Ca2+ ?______ Overall charge of Ca2+? _______

Negative Ions: Anions Anions are negative (-) ions Created when an atom gains / steals an electron Have less protons than electrons

Whole-Class Practice: Anions Cl- Chlorine (Cl) has atomic number 17. # protons in Cl? _______ # electrons in Cl?______ Overall charge of Cl? _______ A Cl- anion is formed when Cl gains one electron. # protons in Cl- ?_______ # electrons in Cl- ?______ Overall charge of Cl- ? _______

Practice: With a partner, answer these questions Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 2+ 3) 2- Cation or Anion? B. 50p+ and 46 e- 1) 2+ 2) 4+ 3) 4- Cation or Anion? C. 15 p+ and 18e- 2) 3+ 2) 3- 3) 5- Cation or Anion? 9/30 – 1st stopped here 9/29 – 5th starts

More Practice: In your Notebook, answer the following questions More Practice: In your Notebook, answer the following questions. Get your work stamped when finished! Directions: Find the number of protons and electrons each ion has, and the overall charge of the ion. Use your periodic table to help you. Use this model to guide you: Ex: Cl- # p+ = ________ # e- = ________ Overall = ____________ Practice Problems: Na+ Br- Be2+ O2- Ba2+ S2- Al3+ P3- B3+ N3-

Ions & Lewis Dot Structures Lesson 3.2B Lewis Dot Structures for Ions

Lesson 3.2B Learning Goals SWBAT define the terms ion, cation, anion SWBAT draw Lewis Dot Structures, in order to represent the valence electrons elements, compounds, and ions.

Valence Electrons Valence electrons are the electrons in the outermost energy levels of an atom. Valence electrons: Have the most energy Are held loosely by the nucleus Can interact with valence electrons on other atoms to form ions or chemical bonds Can be given away or stolen

Valence Electrons and the Periodic Table Valence Electron Rule: Groups of elements on the periodic table have the same number of valence electrons all the way down. EXCEPT for the transition metals

Predicting Ionic Charges Group 1: Lose 1 electron to form 1+ ions H+ Li+ Na+ K+

Predicting Ionic Charges Group 2: Loses 2 electrons to form 2+ ions Be2+ Mg2+ Ca2+ Sr2+ Ba2+

Predicting Ionic Charges Group 13: Loses 3 electrons to form 3+ ions B3+ Al3+ Ga3+

Predicting Ionic Charges Group 14: Lose 4 electrons or gain 4 electrons? Neither! Group 14 elements rarely form ions. They prefer to share.

Predicting Ionic Charges Nitride Group 15: Gains 3 electrons to form 3- ions Phosphide P3- As3- Arsenide

Predicting Ionic Charges Oxide Group 16: Gains 2 electrons to form 2- ions S2- Sulfide Se2- Selenide

Predicting Ionic Charges Group 17: Gains 1 electron to form 1- ions F1- Fluoride Cl1- Chloride Br1- Bromide I1- Iodide

Predicting Ionic Charges Stable Noble gases do not form ions! Group 18:

Atoms WANT 8 so they do anything for The Octet Rule Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 valence electrons Atoms WANT 8 so they do anything for 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Lewis Dot Structures Diagrams that show only valence electrons Shorthand showing information useful for chemical reactions and bonding. Steps to Make LDS: Determine number of valence electrons Arrange valence electrons around elemental symbol Follow electron pairing rule

Lewis Dot Structures An atom’s valence electrons can be represented by Lewis dot notations. 1 valence e- X 2 valence e- 3 valence e- 4 valence e- 5 valence e- 6 valence e- 7 valence e- 8 valence e-

Lewis Dot Structures – Period 2 Lewis dot notations for the valence electrons of the elements of Period 2. lithium Li beryllium Be boron B carbon C nitrogen N oxygen O fluorine F neon Ne worksheet

Independent Practice: In your notebook, draw Lewis Dot Structures for the following elements Ne  K  Ca  Al Li Be  B  C  N 11. All of the elements in period 4 (skip the transition metals, groups 3 – 12).