Writing and Naming formula
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This document discusses writing and naming chemical formulas and ions. It begins by explaining that cations are positively charged ions that migrate to the cathode, while anions are negatively charged ions that migrate to the anode. Examples of common cations and anions are provided. The document then discusses rules for writing formulas for ionic compounds without transition metals, ionic compounds with transition metals, and covalent compounds. It also covers naming conventions for polyatomic ions and provides examples of writing formulas from names and names from formulas.
Writing and Naming formula
- 1. Writing and Naming Chemical Formula JERIC D. LAZO PSU-Bayambang Campus Bachelor of Elementary Education Bayambang, Pangasinan
- 2. Objectives: •We should know first the charges of a Element. The (+) cations and (-) anions. •To be able to write correctly the Chemical formulas and Names •To determined Polyatomic Ions. •Different between Ionic Compound with Transition Metal and the Non-Transition Metal.
- 3. Cations -the ion in an electrolyzed solution that migrates to the cathode; broadly, a positively charged ion. Ex. Name Symbols Hydrogen ion H+ Lithium ion Li+ Sodium ion Na+ Ammonium ion NH4 + Beryllium ion Be2+ Magnesium ion Mg2+ Iron (II) Fe2+ For more example, I provided a Photo copy for list of Cations and Anions. Anions -the ion in an electrolyzed solution that migrates to the anode; broadly, a negatively charged ionName Symbols Chloride Cl- Peroxide O2 2- Hypochlorite ClO- Permanganate MnO4 - Bisulfate HSO4 - Sulfite SO3 2-
- 4. 1. Ionic Compounds Without a Transition Metal. Ionic compounds are formed when a metal gives up its electrons to a non-metal. Basically if the compound contains a metal, it is ionic. But there are different sets of rules for transition metals. A transition metal is an element with an atomic number of 21 to 30, 39 to 48 or 57 to 80. A. So for a compound with any other metal, apply these rules: • The metal ion's name does not change regardless of charge. •The non-metal's name ends in ide. For example: AlCl3 = aluminum chloride Na2S = sodium sulfide K2O = potassium oxide MgH2 = magnesium hydride Notice: how the little numbers (subscripts) do not affect the way we name them
- 5. B. In going backwards (from name to formula), we will have more fun. In such a case the total charge of the (+) and (-) ions in the compound has to be ZERO. Example: What is the correct formula for calcium phosphide? Here, we have to consider the common charges for calcium and phosphorus, which are +2 and -3, respectively. Calcium, if you recall, typically loses two electrons to get a noble gas electron arrangement, and phosphorus needs three more electrons. •Consider the common charges for calcium and phosphorus which Ca+2 and P-3 • One of each would create a sum of 2 + (-3) = -1. •To get a sum of zero, we need three Ca+2 ions and two P-3 for a total of 3(2)+ 2(-3) = 0. •So the answer is Ca3P2. Other examples: potassium oxide : K+1 and O-2 give K2O aluminum bromide Al+3 and Br-1 yield AlBr3.
- 6. Example: •Na2CO3 = sodium carbonate. ( This is a useful chemical in purifying others; it is sometimes called washing soda) •KNO3 = potassium nitrate ( This is an ingredient of gunpowder and it is also found in fertilizer.) To go backwards: Aluminum sulfate This has Al+3 and SO4 -2. To get a sum charge of ZERO, we need two aluminum ions and three sulfates, so the formula becomes Al2(SO4)3. Notice that when there is more than one polyatomic group, we make use of brackets. Aluminum= +3 sulfate = -2 •(+3)+(-2)= 1(it used to be 0) •2(+3)+3(-2)= 0 6+(-6)=0 •Al2(SO4)3 Noted: Superscript of the cation its became the subscript of anions and vice versa.
- 7. C. Polyatomic ions When metals are bonded to polyatomic ions, which consist of two or more atoms with one overall charge, the same rules apply, but you have to learn the names and charges of common polyatomic ions. Polyatomic Ion Name OH-1 hydroxide SO4 -2 sulfate PO4 -3 phosphate NO3 -1 nitrate CO3 -2 carbonate ClO3 -1 chlorate NH4 +1 ammonium HCO3 -1 hydrogen carbonate or Bicarbonate
- 8. Technique for naming Polyatomic Ion • if the polyatomic has smallest no. of atom 2 and 3 then the suffix is –ite but when its add 1 no. of atom (subscript) it became –ate. Ex. Sulfite = SO3 2- and Sulfate = SO4 2- Chlorite= ClO2 - and Chlorate = ClO3 - • If the subscript is 4 we use the prefix per-. Ex. MnH4 = permanganate •If the hydrogen in polyatomic ion appear at first we change hydrogen in prefix Bi-. Ex. Hydrogen sulfite= HSO3 - = bisulfite • if the polyatomic has the lowest subscript we use the prefix hypo-, if the polyatomic has the highest subscript we use the prefix hyper-. Ex. ClO- = Hypochlorite
- 9. 2. Ionic Compounds With a Transition Metal. The only difference here is that we have to specify the charge of the transition metal ion by using a Roman numeral, and keep in mind that a transition metal is an element with an atomic number of 21 to 30, 39 to 48 or 57 to 80.( Those Metals belong in Group B). Roman numeral Charge I +1 II +2 III +3 IV +4 V +5 VI +6 The reason we do this is not for the sake of nostalgia for bygone Roman numerals nor to imitate movie credits. Because transition metals can assume more than one charge, we have to specify which one is involved. Example: Manganese(II) oxide contains Mn+2 and O- 2. So we just need one of each and the formula becomes MnO. •Mn2+ + O-2 •2+(-2)= 0 •MnO (its because we get the LCD of two Chemical charge)
- 10. To go backwards, we need to figure out the charge of the transition metal. Example: What is the correct name of CrCl3 ? The charge of Cr is unknown = x . But chloride = (-1). The sum of the charges has top be zero, so: x +3(-1) = 0. x = 3. Answer: CrCl3 = chromium (III) chloride. Fe2(SO3)3 X(2)+(-2)(3)=0 2x+(-6)=0 2x/2=6/2 X=3 Answer: Fe2(SO3)3 = Iron(III) sulfite.
- 11. 3. Covalent Compounds. These are formed from non-metals that share electrons. Because there are many sharing possibilities between two non-metals, the formula cannot be guessed unless we have a naming system that reveals the number of atoms involved. For this we use a set of prefixes: Prefix Number of atoms Mono 1 di 2 tri 3 tetra 4 penta 5 hexa 6 •The only time we drop a prefix is if the mono is to appear at the beginning of the name. Examples:CO = carbon monoxide ( note we don't say monocarbon monoxide) CO2 = carbon dioxide dinitrogen pentoxide = N2O5. phosphorus trichloride PCl3. Note that none of the above compounds contain a metal. Metals do not form covalent compounds, so we generally don't use prefixes for compounds containing metals.
- 12. More Practice With Naming 1. Name the following: a. NaOH b. Li2S c. FeCl3 d. H2O e. K3N f. CaSO4 2. Write formulae for the following: a. beryllium chloride b. copper (I) oxide (430 only) c. diphosphorus pentoxide d. aluminum carbonate e. ammonium phosphate f. sulfur dioxide Answers 1. a. sodium hydroxide b. lithium sulfide c. iron(III)chloride d. dihydrogen monoxide e. potassium nitride f. calcium sulfate 2. a. BeCl2 b. Cu2O c. P2O5 d. Al2(CO3)3 e. (NH4)3PO4 f. SO2
- 13. Good Job!!! You Made it Credits Powerpoint presentation of: JERIC D. LAZO BEE I-2 Thank you for listening!!!