Symbols & formulas

1. Writing Formulas!

2. It’s so simple… Chemical Formulas only have THREE different parts in them! Symbols Subscripts Coefficients

3. Symbols : Represents an element The first letter is always capitalized, if there is a second letter, it is never capitalized. O = oxygen Cl = chlorine

4. Formulas: Used to represent a group of elements that are connected (a compound/molecule). Tells us what kind of atoms are connected and how many of each atom (element) are present . The order of atoms in the combination is NOT known from the formula. HCl NaCl

5. HCl NaCl LiF KI H Cl Na Cl Li F K I

6. Subscript: The number found after and below an atom’s symbol in a formula. Tells the number of that atoms in the combination (compound) connected with the other atoms. CO 2 How many C? O? C 12 H 22 O 11 How many C? H? O? MgCl 2 How many Mg? Cl ?

7. CO 2 H 2 o NH 3 C 2 H 6 H C N O O O H H H H C C H H H H H H

8. Coefficient: The number found in front of a symbol or formula. Indicates the number of copies (or usually molecules) there are. The atoms/molecules/compounds are separate/not connected! 5 CO 2 10 C 12 H 22 O 11 4 MgCl 2

9. H 2 O H H O 2 H O H

10. CO 2 H 2 o NH 3 C 2 H 6 C O O H O H N H H H C C H H H H H H 3 4 2 2 C O O C O O H O H H O H H O H N H H H C C H H H H H H