Writing Chemical Formulas. Also assigned Ionic Bonding and Ionic Formulas Tutorial and questions

Transcription

1 Writing Chemical Formulas Also assigned Ionic Bonding and Ionic Formulas Tutorial and questions

2 Ions When as atom gains or loses an atom is called an ion. Cation if positively charged or giving electrons away. Anion if negatively charged or accepting electrons.

3 How to predict charges with Lewis Dot All elements move to have a full outer octet, like the Noble Gasses. An outer octet is made from 2 electrons in the s orbit and 6 electrons in the p orbit. Elements can gain or lose electrons to achieve 8 electrons in their valence shell. H H + + e - = e -

4 More Examples: F + e - F N + 3 e - N 3- C C + 4 e - C 4- C e -

5 General Charges X X X X X X X X +1 Many different Charges -2-1 N O B E L G A S E S Many Different Charges

6 Writing Compounds: Sodium and oxygen Na O Na +1 and O 2- These need to add together to equal zero. One must lose electrons and the other must gain electrons. So two sodium s for every oxygen to equal zero. 2(+1) + (-2) = 0 2 Na +1 and O 2- This is written Na 2 O.

7 Example #2: Barium and phosphorous Ba P Ba 2+ and P 3- These must add to equal 0. Therefore 3 bariums and 2 phosphorous are needed. 3(+2) + 2(-3) = 0 3 Ba 2+ and 2 P 3- This is written Ba 3 P 2

8 Polyatomic ions These are groups of atoms that hang around together and have a charge. Hydroxide ion Ammonium ion

9 Here is a trick to name and know about 48 polyatomic ions. Now to name them Like the chart above (base element name) ate BO 3 CO 3 NO 3 1 more oxygen than above Per -(base element name) ate 1 less oxygen than above (base element name ite 2 less oxygen than above Hypo (base element name) - ite PO 4 O SO 4 AsO 4 SeO 4 SbO 4 TeO 4 F ClO 3 BrO 3 IO 3 Noble Gases

10 Polyatomics As is BO 3 3- borate CO 3 2- carbonate NO 3 nitrate PO 4 3- phosphate SO 4 2- sulfate ClO 3 chlorate BO 3 CO 3 NO 3 Lose one oxygen make you want to fight NO 2 nitrite ClO 2 chlorite BO 2 3- borite CO 2 2- carbonite PO 3 3- phosphite SO 3 2- sulfite PO 4 O SO 4 AsO 4 SeO 4 SbO 4 TeO 4 F ClO 3 BrO 3 IO 3 Noble Gases

11 Polyatomics Lose two oxygens and you are out in the cold but still want to fight. ClO hypochlorite BO 3- hypoborite CO 2- hypocarbonite NO hyponitrite PO 2 3- hypophosphite SO 2 2- hyposulfite BO 3 CO 3 NO 3 Gain one oxygen make you want to per ClO 4 perchlorate BO 4 3- perborate CO 4 2- percarbonate NO 4 pernitrate PO 5 3- perphosphate SO 5 2- persulfate PO 4 O SO 4 AsO 4 SeO 4 SbO 4 TeO 4 F ClO 3 BrO 3 IO 3 Noble Gases

12 Other polyatomics that you should know are on the back of your periodic table that you were given.

13 Writing Formulas with polyatomics. Let s write the formula for sodium and phosphate. Na + PO 3-4 Remember that these must add to equal zero. (+1) + (-3) = Na + PO Na 3 PO 4

14 Writing Formulas with polyatomics. Let s write the formula for calcium and nitrate. Ca 2+ NO - 3 Remember that these must add to equal zero. (+2) + (-1) = Ca 2+ NO 3 - Because there are two nitrates needed to balance out the charge of the calcium parenthesis are used to keep the group together and denote that two groups of nitrate are needed to balance the charge of the calcium. Ca(NO 3 ) 2

15 Writing Formulas with polyatomics. Let s write the formula for barium and phosphate. Ba 2+ PO 3-4 Remember that these must add to equal zero. (+2) + (-3) = Ba + PO 4 3- Because there are two phosphates needed to balance out the charge of three bariums parenthesis are used to keep the group together and denote that two groups of phosphate are needed to balance the charge of the three bariums. Ba 3 (PO 4 ) 2

16 Writing Formulas with polyatomics. Let s write the formula for lead (IV) carbonate. The Roman Number (IV) tells the charge of the lead. The Roman number always tells the charge of the positive ion. Pb 4+ CO 2-3 Remember that these must add to equal zero. Careful! This must happen with the lowest numbers possible! (+4) + (-2) = Pb 4+ CO 3 2- Because there are two carbonate ions needed to balance out the charge of on lead (IV) ion parenthesis are used to keep the group together and denote that two carbonate ions are needed to balance the charge of the lead (IV) ion. Pb(CO 3 ) 2

17 Writing Formulas with polyatomics. Let s write the formula for aluminum and oxalate. Al 3+ C 2 O 2-4 Remember that these must add to equal zero. (+3) + (-2) = Al 3+ C 2 O 4 2- Because there are three oxalate ions needed to balance out the charge of two aluminum parenthesis are used to keep the group together and denote that three groups of oxalate are needed to balance the charge of the two aluminum. Al 2 (C 2 O 4 ) 3

18 Keep Practicing! Keep Up! Don t forget to take notes!