Cations and Anions: Part 1 2016 Mrs. Crowley H. Chemistry

Stoplight method Green/Yellow/Red Light: Green = I know it so well that I could teach it to someone else Yellow = I’m a little shaky, but I think I’ve got the gist of it. Red = I’ve very little experience with this concept and/or never heard of this before.

Rank each of the following objectives with the “stoplight” method. I know the difference between a cation and an anion. I can predict the charges of ions based on their location on the periodic table.

Octet Rule: A review A stable arrangement of 8 valence electrons in the outer most energy level. All noble gases except Helium have it. All other elements on the periodic table want to have an octet like the noble gases. In order to do this, atoms will gain or lose electrons in order to get that octet.

When atoms MAKE bonds, they do it to become more stable. 3 Main types of Bonds When atoms MAKE bonds, they do it to become more stable. 3 main types of bonding: covalent, polar, and ionic. When electrons MOVE from one atom to another, this is called an ionic bond. When 2 atoms SHARE electrons, this is called covalent bonding. When 2 atoms SHARE UNEQUALY, this is called a polar bond.

Releasing Energy during a chemical reaction: Exothermic Reaction Exothermic Reactions Chemical reactions occur so that atoms can be more like noble gases and become MORE stable, thus releasing energy during a reaction. Releasing Energy during a chemical reaction: Exothermic Reaction

Exothermic reactions: release energy into the environment Why is there a small bump? You have to push the atoms together in order to get the reactions started. The small bump of energy needed is called “activation energy.” This is similar to starting a fire with a match. Wood is flammable, but you must combine the organic material with oxygen to get it started. Activation energy Starting energy Overall decrease in energy Ending energy

Endothermic Reactions This is an overall UPWARD movement in overall energy. The reactants have a lower amount of energy than the products. This reactions REQUIRES energy from the surrounding environment. It absorbs energy from the environment. These reactions FEEL cool. Ending energy Starting energy

A little more: endothermic vs. exothermic http://www.youtube.com/watch?v=L-G7pLufXAo

Examples! https://www.youtube.com/watch?v=cESHUY8QSXY https://www.youtube.com/watch?v=euQUgp5AY- Y&feature=iv&src_vid=CWMATrOatRw&annotation_id=annotation_ 693441

All atoms want to be like noble gases For example: Potassium (K) would like to be like the closest noble gas to it…. Argon Another example: Iodine (I) would like to be like the closest noble gas to it…. Xenon

Cations: Positively charged ion formed when an atom LOSES electrons Naming: Cations keep their name when they lose an electron. When sodium loses an electron to become a cation, we call it the “sodium” ion. Symbol: Na+ superscript

Example #1: sodium Notice that this atom has 1 valance electron. Sodium has 2 choices: lose 1 electron to look like Neon Or gain 7 more electrons to be like Argon. Atoms are lazy…they take the easiest option! Sodium will LOSE 1 ELECTRON! 11 p+

What does sodium look like now? Still has 11 protons Example #1: sodium What does sodium look like now? Still has 11 protons Now has only 10 electron Protons are positive Electrons are negative (+11)+(-10) = +1 charge 11 p+

The process: All atoms want to be like the closest noble gas to it. Sodium wants to be like Neon. Sodium’s electron configuration: 1s2 2s2 2p6 3s1 Neon’s electron configuration: 1s2 2s2 2p6 So Na must lose ONE electron to be like Neon

More about the process: Where does the positive charge come from? (1) Start with neutral Na atom. (2) Then lose (subtract) negative e-. (3) Answer is ion’s charge. 0 - (-1) = +1

Try this one on your own: What is the charge of the Sr cation? (atomic # 38)

Cation Periodic trends Groups 1 and 2 (alkali metals and alkaline earth metals) have elements that easily form cations because of their low ionization energies. Metals can ONLY FORM CATIONS! That’s right…all metals are LOSERS! :D

Anions: Negatively charged ion formed when an atom GAINS electrons Naming: Anions from the periodic table are named by adding “-ide” to the name of the element gaining the electrons. Examples: Fluorine becomes “fluoride” F- Chlorine becomes “chloride” Cl- superscripts

Has 17 protons and 17 electrons. Draw the electrons in: Example #2: Chlorine Chlorine: atomic #17 Has 17 protons and 17 electrons. Draw the electrons in: 17 p+ Remember: 1st ring: 2 electrons max 2nd ring: 8 electrons max 3rd ring: 18 electrons max

What does chlorine want to do? Chlorine has 2 choices: Lose all 7 valence electron Gain 1 more valence electron Much easier to just gain 1 17 p+

The process: Fluorine wants to become like the closest noble gas to it, NEON. F: 1s2 2s2 2p5 Ne: 1s2 2s2 2p6 So fluorine must gain ONE electron to be like neon and will be called “fluoride.”

Where does the negative charge come from? (1) Start with neutral F atom. (2) Then gain (add) negative e-. (3) Answer is ion’s charge. 0 + (-1) = -1

What is the charge of the S anion? What is it called? Try one on your own: What is the charge of the S anion? What is it called?

Calcium Bromine Lithium Magnesium Now a bit of practice with cations AND anions. Figure out what these atoms will do: Calcium Bromine Lithium Magnesium

Periodic trends to be aware of: The Nitrogen group, Oxygen group, and Halogens all prefer to GAIN electrons because it would be easer for these elements to gain electrons to be like a noble gas. Once you tuck UNDER the ladder that separates metals from nonmetals, this trend gets tricky. You must know where that ladder is. Bottom line: Metals LOSE electrons Nonmetals GAIN electrons Metalloids are tricky…some gain, some lose.

And one more thing… Transition metal ions have varying charges, but will typically have a 2+ or 3+ charge You will be given the charges for these ions when you have to use them.

Stoplight method Green/Yellow/Red Light: Green = I know it so well that I could teach it to someone else Yellow = I’m a little shaky, but I think I’ve got the gist of it. Red = I’ve very little experience with this concept and/or never heard of this before.

Rank each of the following objectives with the “stoplight” method. I know the difference between a cation and an anion. I can predict the charges of ions based on their location on the periodic table.