**How to convert from standard notation to scientific notation**

- Find the first number between 1 and 10
- Place a decimal point and write remaining numbers
- Add x 10 to the right of the number in 2
- Count number of places needed to move decimal to create the original number
- count right = (+) exponent
- count left = (-) exponent

- Place the number you found in 4 as an exponent on the 10.
- (+) exponent = counted right
- (-) exponent = counted left

**How to convert from scientific notation to standard notation**

- Determine the exponent
- (+) move decimal right
- (-) move decimal left

- Move decimal in number before x 10 the number in 1 and place a decimal
- Add zero where no number exists

### Significant Figures Rules

Leading zeros are not significant

- 0.0032

Trailing zeros are signficiant

- 0.003200
- 10.00

Zeros inbetween real numbers are significant

- 101
- 0.00101

If the last place is a decimal, then all numbers are significant

- 1250.

If a number is exact, then there are an unlimited number of significant figures.

- Includes defined quantities

### Tips on Writing Molecular, Total and Net Ionic Equations

**Given: BaS _{(aq)} + NH_{4}Cl_{(aq)} →**

Find Molecular, Total and Net Ionic Equations

- Determine products
- BaS
_{(aq)}+ NH_{4}Cl_{(aq)}→ BaCl_{2}+ (NH_{4})_{2}S

- BaS
- Balance molecular equation
- BaS
_{(aq)}+ 2NH_{4}Cl_{(aq)}→ BaCl_{2}+ (NH_{4})_{2}S

- BaS
- Determine Solubility of Products
- BaS
_{(aq)}+ 2NH_{4}Cl_{(aq)}→ BaCl_{2 (aq)}+ (NH_{4})_{2}S_{(aq)}

- BaS
- If soluble (aq) break into ions. Everything else stays together.
- REMEMBER:
- ions must have a charge
- coefficients distribute just like in math
- subscripts used for balancing become coefficients

- Total Ionic Equation
- Ba
^{2+}_{(aq)}+ S^{2-}_{(aq)}+ 2NH_{4}^{+}_{(aq)}+ 2Cl^{-}_{(aq)}→ Ba^{2+}_{(aq)}+ 2Cl^{-}_{(aq)}+ 2NH_{4}^{+}_{(aq)}+ S^{2-}_{(aq)}

- Ba

- REMEMBER:
- Lightly cross out what looks the same on both sides.
- NOTE: If everything is crossed out - rewrite left side yields NR.

- Net Ionic Equation
- Ba
^{2+}_{(aq)}+ S^{2-}_{(aq)}+ 2NH_{4}^{+}_{(aq)}+ 2Cl^{-}_{(aq)}→ NR

- Ba