Write down the outermost electronc configuration of alkali metals. How will you justify their placement in group 1 of the periodic table?

Explanation

### Step-by-Step Solution:

1. **Identify the Alkali Metals**:
The alkali metals are a group of elements found in Group 1 of the periodic table. They include:
- Lithium (Li)
- Sodium (Na)
- Potassium (K)
- Rubidium (Rb)
- Cesium (Cs)
- Francium (Fr)

2. **Write the Outermost Electronic Configuration**:
The outermost electronic configuration of alkali metals can be expressed in the form of \( ns^1 \), where \( n \) represents the principal quantum number corresponding to the outermost shell. Here are the configurations for each alkali metal:
- Lithium (Li): \( 1s^2 2s^1 \) → Outermost configuration: **\( 2s^1 \)**
- Sodium (Na): \( 1s^2 2s^2 2p^6 3s^1 \) → Outermost configuration: **\( 3s^1 \)**
- Potassium (K): \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 \) → Outermost configuration: **\( 4s^1 \)**
- Rubidium (Rb): \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^6 5s^1 \) → Outermost configuration: **\( 5s^1 \)**
- Cesium (Cs): \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^6 5s^2 5p^6 6s^1 \) → Outermost configuration: **\( 6s^1 \)**
- Francium (Fr): \( 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^6 5s^2 5p^6 6s^2 6p^6 7s^1 \) → Outermost configuration: **\( 7s^1 \)**

3. **Justify Their Placement in Group 1**:
The justification for the placement of alkali metals in Group 1 of the periodic table is based on their electronic configuration. All alkali metals have one electron in their outermost shell (valence shell), which is represented by the \( ns^1 \) configuration. This single valence electron is responsible for their similar chemical properties, such as high reactivity and the tendency to lose one electron to form positive ions (cations) with a charge of +1. Therefore, due to the presence of only one valence electron in the outermost shell, they are classified in Group 1.

### Summary:
- Outermost electronic configurations:
- Li: \( 2s^1 \)
- Na: \( 3s^1 \)
- K: \( 4s^1 \)
- Rb: \( 5s^1 \)
- Cs: \( 6s^1 \)
- Fr: \( 7s^1 \)
- Justification: Presence of one valence electron in the outermost shell places them in Group 1.