Borax is written as

Options

A. `Na_(2)[B_(4)O_(5)(OH)_(4)]*8H_(2)O`
B. `Na_(2)B_(4)(OH)_(7)O_(2)*3H_(2)O`
C. `Na_(2)OB_(4)O_(8)H_(2)`
D. `Na_(2)B_(4)O_(17)H_(2)O`

Answer

To determine how borax is written, we can break down the information provided in the question and the video transcript step by step.

### Step-by-Step Solution:

1. **Identify the Chemical Composition of Borax**:
- Borax is a compound that contains boron, sodium, oxygen, and hydrogen. It is also known as sodium borate or disodium tetraborate.

2. **Common Forms of Borax**:
- The most common form of borax is borax decahydrate, which has the chemical formula Na2B4O7·10H2O. Other forms include borax pentahydrate and borax anhydrous.

3. **Count the Atoms in Borax**:
- In the decahydrate form, borax consists of:
- 2 Sodium (Na) atoms
- 4 Boron (B) atoms
- 7 Oxygen (O) atoms (from Na2B4O7)
- 10 Hydrogen (H) atoms (from 10 water molecules)
- Therefore, the total number of oxygen atoms is 7 from the borate part and 10 from the water, giving a total of 17 oxygen atoms.

4. **Write the Chemical Formula**:
- The chemical formula for borax can be expressed as Na2B4O7·10H2O or Na2B4O5(OH)·8H2O. Both formulas represent the same compound but in different forms.

5. **Evaluate the Options Given**:
- The options provided in the question are:
- Na2B4O5(OH)·4·8H2O
- Na2B4(OH)7O2·3H2O
- Na2O·B4O8·H2
- Na2B4O17·H2O
- We need to check which of these options matches the composition we identified.

6. **Match with the Correct Formula**:
- After analyzing the options:
- The correct formula for borax is **Na2B4O5(OH)·8H2O**.
- This matches our earlier findings regarding the number of atoms.

### Conclusion:
Thus, borax is correctly written as **Na2B4O5(OH)·8H2O**.