writing chemical formulas
TRANSCRIPT
![Page 1: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/1.jpg)
PRESENTED BY: DAVE LESTER C. GALANG
Writing Chemical Formulas
![Page 2: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/2.jpg)
is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line ofchemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
![Page 3: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/3.jpg)
The chemical formula of a covalent molecular compound tells us the number of atoms of each element present in the compound. E.g. Water H2O -The formula tells us that there are 2 Hydrogen atoms and 1 oxygen atom present in each water molecule.
![Page 4: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/4.jpg)
The chemical formula of a covalent network tells us the ratio of the elements present. E.g. Silicon dioxide, SiO2 structure-The formula tells us there are 2 silicon atoms present for every 1 oxygen atom.
![Page 5: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/5.jpg)
The chemical formula of an ionic compound tells us the ratio of the elements present. E.g. Sodium chloride, NaCl – The formula tells us there is one ion of sodium for every one ion of chlorine
Chloride ion Sodium ion
Sodium chloride, NaCl, structure
![Page 6: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/6.jpg)
1. CHEMICAL FORMULA FOR ELEMENTS
The chemical formula of an element is simply its’ symbol
e.g. Magnesium Mg Iron Fe Phosphorus P Argon Ar
![Page 7: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/7.jpg)
Whenever we write the chemical formula of these elements we put a subscript ‘2’ beside them
e.g. Iodine I2
I n Oxygen O2
O ctober Chlorine Cl2
C hildren Bromine Br2
B uy Nitrogen N2
N asty Hydrogen H2
H alloween Fluorine F2
F oods
![Page 8: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/8.jpg)
2.USING VALENCY
The valency of an atom or ion is the number of electrons it shares, loses or gains in a chemical reaction to become stable i.e. the number of bonds it forms with other atoms
Table: Group number 1 2 3 4 5 6 7 0 Valency 1 2 3 4 3 2 1 0
![Page 9: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/9.jpg)
We can follow a set of simple rules to write chemical formula:
1. Write symbols of elements present in compound
2. Put valency above each symbol
3. Cross valency over (swap and drop)
4. Cancel down ratio if necessary 5. Write correct chemical
formula
![Page 10: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/10.jpg)
Example
1. Sodium chloride 1. Na Cl 2. Na1 Cl1
3. Na1 Cl1 4. (Not needed) 5. NaCl
![Page 11: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/11.jpg)
Example 2. Calcium bromide 1. Ca Br 2. Ca2 Br1
3. Ca1 Br2 4. (Not needed) 5. CaBr2
![Page 12: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/12.jpg)
3. ROMAN NUMERALS
Some elements, particularly the transition metals in the centre block of the periodic table can have more than one valency.
![Page 13: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/13.jpg)
Roman Numeral Valency I 1 II 2 III 3 IV 4 V 5 VI 6
![Page 14: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/14.jpg)
Example 1. Copper(II) chloride 1. Cu Cl 2. Cu2Cl1
3. Cu1 Cl2 4. CuCl2
![Page 15: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/15.jpg)
Example 2. Iron(III)fluoride 1. Fe F 2. Fe3 F1
3. Fe1 F3 4. FeF3
![Page 16: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/16.jpg)
4. PREFIXES
In the names of some compounds the ratio of atoms present can be indicated by prefixes.
Prefix Meaning Mono 1 Di 2 Tri 3 Tetra 4 Penta 5 Hexa 6
![Page 17: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/17.jpg)
Examples Carbon monoxide CO
Nitrogen dioxide NO2
Phosphorus trichloride PCl3
Phosphorus pentachloride PCl5
Dinitrogen tetroxide N2O4
![Page 18: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/18.jpg)
5.Polyatomic Ions
Ions formed by more than one type of element
Atoms of different elements held together by covalent bonds
Atoms always stay together and collectively have a single charge
Do not always have “-ide” endingex: NH4
1- = ammonium ion CO3
2- = carbonate
![Page 19: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/19.jpg)
Example
1.Ammonium Nitride2. Sodium Carbonate3. Ammonium Phosphate4. Magnesium Phosphate
![Page 20: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/20.jpg)
6. IONIC FORMULA
The ionic formula shows the charges of the ions present in an ionic substance.
![Page 21: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/21.jpg)
GROUP NUMBER
12345670
VALENCY
1234321
0
CHARGE ON ION
1+ 2+ 3+ 4 3- 2- 1-
0
![Page 22: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/22.jpg)
Example
1 Lithium Oxide2. Potassium Nitride3. Sodium Chloride4. Aluminum Oxide
![Page 23: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/23.jpg)
QOUTES FOR TODAY
THE CHEMICAL COMPOSITION OF
YOUR TEARS CHANGE, DEPENDING ON YOUR EMOTION
![Page 24: writing chemical formulas](https://reader035.vdocuments.net/reader035/viewer/2022062522/5872253e1a28ab3b7a8b50a1/html5/thumbnails/24.jpg)
THANK YOU