1 / 19

Chemistry II

Chemistry II. Ionic Compounds Naming and Writing Formulas. Review of how ions are formed. Octet rule – elements are most stable when they have 8 valence electrons Elements can gain or lose valence electrons in order to have 8. sodium ion Na +. e -. e -. e -. e -. 11 p +. e -. e -.

tasha-chase
Download Presentation

Chemistry II

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chemistry II Ionic Compounds Naming and Writing Formulas

  2. Review of how ions are formed • Octet rule – elements are most stable when they have 8 valence electrons • Elements can gain or lose valence electrons in order to have 8.

  3. sodium ion Na+ e- e- e- e- 11p+ e- e- e- e- e- e- Formation of Cation sodium atom Na e- e- e- e- e- e- loss of one valence electron 11p+ e- e- e- e- e- e-

  4. chloride ion Cl1- e- e- e- e- e- e- e- e- 17p+ e- e- e- e- e- e- e- e- e- e- Formation of Anion chlorine atom Cl gain of one valence electron e- e- e- e- e- e- e- e- 17p+ e- e- e- e- e- e- e- e- e- e-

  5. Bonding • Chemical Bond • attractive force between atoms or ions that binds them together as a unit • Purpose bonds formFORM IN ORDER TO …. • To decrease potential energy (PE) • To Increase stability Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  6. Why bonds form… • Atoms of many elements are more stable as they are bonded to other atoms. • Energy is released into surroundings resulting in a system with lower energy. • An atom’s electron configuration determines how it interacts with other atoms • Particularly valence electrons

  7. What are ionic bonds? • Chemical interactions(attractions) between charged particles - Called Electrostatic attraction • Result from a transfer of electrons making a cation and anion

  8. Crystal Lattice NaCl 1:1 Ratio Ionic compounds do not exist as single molecules but rather as numerous units organized in a stable crystal .

  9. Participants • Ionic bonds form between metals and non-metals • Metals have lower ionization energies and therefore more readily “give away” electrons – Form Cations • Non-metals have high electron affinities and therefore more readily accept electrons. – Form Anions • New Term- Oxidation Number = ion charge • sodium’s oxidation number is 1+, Chlorine’s is 1-

  10. Naming Ionic Compounds • Cation – borrows name from element • Always listed first • Anion – ends in “ide” (with the exception of polyatomic ions) • Always listed second • Examples • NaCl – sodium chloride • ZnS – zinc sulfide • Mg3N2 – magnesium nitride • SPELLING COUNTS!

  11. Step 3: AlCl 3 Writing Ionic Formulas Criss-Cross Rule Example: Aluminum Chloride Step 1: Write symbols & charge of elements. Write charges ABOVE the letters 1- Al Cl 3+ Step 2: Al Cl 1 3 criss-cross charges as subscripts combine as formula unit *“1” is never shown *get rid of charges on top Step 4 : *simplify if needed

  12. Variable Charge Ions • Some elements in the transition metals can form more than one type of ion. Sometimes they may lose 2, 3, 4 or even more electrons in order to bond with another element. • So these metals can form +2, +3 ,+4 etccationsin one compound but have a different charge in another compound. In order to tell them apart we name them differently.

  13. Writing the formula • When given the name of the compound, the Roman numeral after the metal tells us the CHARGE of the metal. • Copper II Chloride – means Cu+2 Cl-1 • Follow the same steps as before >>>> 1. Write out the charges 2. Criss-cross 3. Combine as a formula unit (get rid of charges on top) 4. Simplify if needed

  14. Cu Fe A. To name, given the formula: • Figure out charge on • cation. 2. Write name of cation. 3. Write Roman numerals in ( ) to show cation’s charge. Stock System of nomenclature 4. Write name of anion. iron oxide Fe2+ Fe? iron (II)oxide FeO O2– iron oxide Fe? O2– Fe2O3 Fe? Fe3+ O2– O2– Fe3+ iron (III)oxide CuBr copper bromide Cu? Br1– copper (I)bromide Cu1+ CuBr2 copper bromide Br1– copper (II)bromide Cu2+ Cu? Br1–

  15. When writing the formula for an ionic compound with a polyatomic ion, follow the same rules but treat the polyatomic ion as a single unit.

  16. Writing Formulas w/Polyatomic Ions Polyatomic Ion: a group of atoms that stay together and have a single, overall charge. BaSO4 barium sulfate Ba2+ and SO42– Mg(NO2)2 Mg2+ and NO21– magnesium nitrite NH4ClO3 ammonium chlorate NH41+ and ClO31– Sn(SO4)2 tin (IV) sulfate Sn4+ and SO42– ? Fe2(Cr2O7)3 Fe3+ and Cr2O72– iron (III) dichromate ammonium nitride (NH4)3N NH41+ and N3–

  17. Rules for Parentheses Parentheses are used only when the following two condition are met: • There is a (polyatomic ion) present and… • There are two or more of that in the formula. Examples: NaNO3 NO31-, but there is only one of it. Co(NO3)2NO31- there are two of them (NH4)2SO4NH41+there are two of them; SO42-there is only one of it. Co(OH)2 OH1-there are two of it. Al2(CO3)3 CO32-there are three of them. NaOH OH1-there is only one of it.

  18. Pattern to Memorizing Nomenclature XY “-ide” XYO4 XYO3 XYO2 XYO “per___-ate” “-ate” “-ite” “hypo___-ite” 1 more oxygen normal 1 less oxygen 2 less oxygen

  19. Physical Characteristics • Physical characteristics result from the strong attractive forces between charged particles and the crystal structure • High melting and boiling points • Lots of energy necessary to break strong bonds • Solid at room temperature • Stable crystal structure • Hard and brittle • Crystal allows compound to withstand great force • Too much force causes repulsive forces to overpower attractive forces and the crystal shatters • Conduct electricity when melted and dissolved in water • Charged particles that are able to move

More Related