Analyse the given information and answer the following questions.
A=Na=2,8,1
B=Mg=2,8,2
C=H=1
D=Cl=2,8,7
What will be the general formula when B and D react?

Options

A. `BD_2`
B. `B_2D`
C. BD
D. `BD_4`

Explanation

To determine the general formula when B (Magnesium, Mg) and D (Chlorine, Cl) react, we can follow these steps:

### Step 1: Identify the Electron Configuration
- B (Magnesium, Mg) has the electron configuration of 2, 8, 2.
- D (Chlorine, Cl) has the electron configuration of 2, 8, 7.

### Step 2: Determine the Valency
- Magnesium (Mg) is a metal and will lose its two outermost electrons to achieve a stable electron configuration (noble gas configuration). Therefore, its valency is +2.
- Chlorine (Cl) is a non-metal and needs one more electron to complete its outer shell (to achieve noble gas configuration). Therefore, its valency is -1.

### Step 3: Write the Ionic Compound
- When magnesium reacts with chlorine, magnesium will lose 2 electrons, and each chlorine atom will gain 1 electron.
- Since one magnesium atom can provide 2 electrons, it will require 2 chlorine atoms to balance the charge.

### Step 4: Combine the Valencies
- The formula can be derived by combining the valencies:
- Magnesium (Mg) has a valency of +2.
- Chlorine (Cl) has a valency of -1.
- To balance the charges, we need 2 chlorine atoms for every 1 magnesium atom.

### Step 5: Write the Final Formula
- Therefore, the formula for the compound formed when magnesium and chlorine react is MgCl₂.

### Final Answer
The general formula when B (Mg) and D (Cl) react is **MgCl₂**.