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Presentation on theme: "LIFE IS A SERIES OF THINGS YOU’RE NOT QUITE READY FOR."— Presentation transcript:


2 REVIEW 1.What are the main subatomic particles that make up the atom? 2.What is the charge on each of the particles? 3.Which of the particles is most massive? Least massive? 4.What isotope is used as the standard in establishing the atomic mass scale? 5.The atomic weight of chlorine is reported as 35.5, yet no atom of chlorine has this mass. Explain.

3 6. How many protons, neutrons, and electrons are in the following atoms? a. 28 Si b. 60 Ni c. 85 Rb d. 128 Xe

4 7. Write the electron configuration for the following atoms: a. Boron, B b. Sodium, Na c. Silicon, Si d. Calcium, Ca 8. How many valence electrons does each atom in #7 have?

5 IONS AND IONIC COMPOUNDS One way atoms can form chemical compounds is through the loss and gain of electrons. Note: “the nucleus of an atom is unchanged in chemical processes, but atoms can readily lose or gain electrons.” - Brown and LeMay- If an atom is neutral to begin with, it becomes electrically charged if it loses or gains electrons. The resulting charged particles are called ions.

6 Keep in mind the “octet rule” when talking about bonding. A full outer shell represents a stable configuration. If the first shell is the outer shell, it can hold 2 electrons. In any other shell, 8 is the maximum number of electrons that can exist in the outer shell. Let’s consider the reaction between sodium and chlorine: Na + Cl --> Na + Cl - Sodium loses and electron to become a sodium ion with a positive charge. Na (1s 2 2s 2 2p 6 3s 1 ) --> Na + (1s 2 2s 2 2p 6 ) + e - Positive ions are called cations. 8 electrons in outer shell

7 Chlorine gains an electron. Cl (1s 2 2s 2 2p 6 3s 2 3p 5 ) + e - --> Cl - (1s 2 2s 2 2p 6 3s 2 3p 6 ) Note: negative ions are called anions. Or Na --> Na + + e - Cl + e - --> Cl - Adding the two equations Na + Cl --> Na + Cl - Note: the net charge on an ion is represented with a superscript. 8 electrons in outer shell

8 Give the chemical symbols, including mass numbers for the following ions: a.An ion with 22 protons, 26 neutrons, and 19 electrons. b.The ion of sulfur that has 16 neutrons and 18 electrons. c.The ion of selenium with 34 protons and 36 electrons

9 In predicting the charge on a simple ion, a good rule of thumb is that atoms gain or lose electrons to end up with the same number of electrons as the nearest noble gas on the periodic table. a. Group I ions (alkali metals) have +1 charges. b. Group 2 ions (alkaline earth metals) have +2 charges. c. Group 6 ions (nonmetals) have -2 charges. d. Group 7 ions (halides) have -1 charges. e. There is no simple way to predict the charges of the transition metals.

10 Another way of expressing the rules is that metals will usually react by losing electrons, and nonmetals will react by gaining electrons.

11 Although we write the formulas for ionic compounds as the simple formulas, for example, NaCl (the simplest whole number ratio), ionic compounds usually exist as three dimensional solids. Using sodium chloride as an example

12 Some characteristics of ionic compounds: 1.They are solids at room temperature. 2.They are held together by electrostatic forces of attraction between oppositely charged ions. 3.They have very high melting points. 4.All ionic compounds form crystals. 5.Ionic substances are hard, brittle solids. 6.When dissolved in water, the solutions are good conductors of electricity.

13 Ions in water.

14 NAMING IONIC COMPOUNDS Cations formed from metal atoms take the name of the metal. Na + - sodium ion Ca +2 - calcium ion Al +3 - aluminum ion In the case of transition metal ions that can form ions of different charges, the charge is given as a Roman numeral. Fe +2 - iron (II) ion Fe +3 - iron (III) ion

15 Anions formed from single nonmetal ions have names formed by replacing the ending of the name of the element with -ide. Br - - bromide ion Cl - - chloride ion S -2 - sulfide ion N -3 - nitride ion A few simple polyatomic anions also take the -ide ending. OH - - hydroxide ion CN - - cyanide ion O 2 -2 - peroxide ion

16 To name compounds, you combine the name of the cation (first) with the name of the anion, dropping “ion”. Examples: NaCl sodium chloride BaF 2 barium fluoride (note: charges have to balance) NaCN sodium cyanide KOH potassium hydroxide AgCl silver chloride FeCl 2 iron (II) chloride FeCl 3 iron (III) chloride

17 There are some polyatomic anions that you will just have to learn the names. NO 3 - nitrate ion NO 2 - nitrite ion SO 4 -2 sulfate ion SO 3 -2 sulfite ion CO 3 -2 carbonate ion PO 4 -3 phosphate ion There is one polyatomic cation you need to know the name. NH 4 + ammonium ion

18 We would use the names of these polyatomic anions in naming our compounds. Na 2 SO 4 - sodium sulfate (again, charges have to balance) NaHCO 3 - sodium hydrogen carbonate KNO 3 - potassium nitrate BaSO 4 - barium sulfate Ca(NO 2 ) 2 - calcium nitrite Li 3 PO 4 - lithium phosphate NH 4 Cl - ammonium chloride

19 chemistry-of-cars-cynthia-chubbuck


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