Tuesday, Jan. 14 th : “A” Day Wednesday, Jan. 15 th : “B” Day Agenda  Homework Questions?/Collect  Sec. 5.1 Quiz: “Simple Ions”  Begin Section 5.2: “Ionic Bonding and Salts” Salt, lattice energy  ACT Practice We will finish section 5.2 next time…

Homework Problems/Questions?  In-class assignment: pg. 165: #1-13  Homework: “Ions and Subatomic Particles” WS

Quiz 5.1: “Simple Ions”  You may use your notes, your book, and your periodic table to complete the quiz on your own.  Quiz Corrections: #3: 3s 6 should be 3p 6 #8 and #9: The term “ionize” means to lose or gain electrons to form an ion. Take your time, this quiz is a little tricky… Good Luck!

Section 5.2: “Ionic Bonding and Salts”  Because opposite charges attract, cations and anions should attract one another.  This is exactly what happens when an ionic bond forms.

Ionic Bonds Form Between Ions of Opposite Charge  Remember, An alkali metal, such as sodium, will LOSE 1 electron to form a 1 + ion (cation) Na + A halogen, such as chlorine, will GAIN 1 electron to form a 1 - ion (anion) Cl -

Ionic Bonds Form Between Ions of Opposite Charge  The force of attraction between the 1 + charge on the sodium cation and the 1  charge on the chloride anion creates the ionic bond in sodium chloride.  Sodium chloride is a salt.

Ionic Bonds Form Between Ions of Opposite Charge  Salt: an ionic compound that forms when a metal atom or a positive radical replaces the hydrogen of an acid.  Plain English: the scientific name given to thousands of different ionic compounds. Examples of salts: KCl: Potassium chloride AlCl 3 : Aluminum chloride

Ionic Bonds Form Between Ions of Opposite Charge  All salts are electrically neutral ionic compounds that are made up of cations and anions held together by ionic bonds in a simple, whole- number ratio.  However, the attractions between the ions in a salt do not stop with a single cation and a single anion.  One cation attracts several anions, and one anion attracts several cations.  They are all pulled together into a tightly packed crystal structure.

Transferring Electrons Involves Energy Changes  Remember, ionization energy is the energy required to remove the outermost electron from an atom.  The equation below shows this process for sodium. Na + energy  Na + + e  (Energy added = ENDOTHERMIC process)

Transferring Electrons Involves Energy Changes  Remember, electron affinity is the energy change that occurs when a neutral atom gains an electron.  Some elements, such as chlorine, easily accept electrons and energy is released when an electron is added. Cl + e   Cl  + energy (Energy released = EXOTHERMIC process)

Transferring Electrons Involves Energy Changes  The energy released when chlorine accepts an electron is less than the energy required to remove an electron from a sodium atom.  Adding and removing electrons is only part of forming an ionic bond.  The rest of the process of forming a salt supplies enough energy to make up the difference so that the overall process releases energy.

Salt Formation  The process of forming the salt sodium chloride can be broken down into five steps: 1. Energy is added to make solid sodium metal into a gas. Na(solid) + energy  Na(gas) 2. Energy is added to remove an electron from the gaseous sodium atom to make an ion. Na(gas) + energy  Na + (gas) + e 

Salt Formation 3.Chlorine gas exists as 2 chlorine atoms bonded together, so energy must be added to separate the chlorine atoms so that they can react with sodium. Cl–Cl(gas) + energy  Cl(gas) + Cl(gas)  The first three steps have all been endothermic (energy added) and have produced sodium cations and chlorine atoms. Cl Na +

Salt Formation  The last 2 steps will be exothermic (energy released) and will produce chloride anions and the salt NaCl. Cl - NaCl 4. An electron is added to a chlorine atom to form an anion. This step releases energy. Cl(gas) + e   Cl  (gas) + energy

Salt Formation 5. When a cation and anion form an ionic bond, it is an exothermic process and energy is released. Na + (gas) + Cl  (gas)  NaCl(solid) + energy  The last step is the driving force for salt formation because of the energy released.

Formation of Sodium Chloride

Lattice Energy  Lattice Energy: the energy associated with constructing a crystal lattice relative to the energy of all constituent atoms separated by infinite distances.  Plain English: the energy released during salt formation when ionic bonds are formed.

Lattice Energy  With the release of the lattice energy, the crystal lattice structure has lower potential energy than the neutral atoms that form the salt.  Without this energy, there would not be enough energy to make the overall process spontaneous.

ACT Practice  During the 2 nd semester, we will practice ACT- type problems to help foster critical thinking and problem solving skills.  Please read the passage “The Modern Periodic Table” and completed the associated questions.  We will go over them once everyone is finished, so hold on to them.  Yes, this is for a grade!