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

The alkali metals are located in Group 1 of the periodic table. The outermost electronic configuration of alkali metals can be represented as ns^1, where 'n' represents the principal quantum number of the valence shell.

Here's the outermost electronic configuration of alkali metals:

• Lithium (Li): 1s^2 2s^1
• Sodium (Na): 1s^2 2s^2 2p^6 3s^1
• Potassium (K): 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1
• Rubidium (Rb): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 5s^1
• Cesium (Cs): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 5s^2 5p^6 6s^1
• Francium (Fr): 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 4p^6 4d^10 4f^14 5s^2 5p^6 5d^10 6s^2 6p^6 7s^1

Justification for their placement in Group 1 of the periodic table:

1. Similar Outermost Electron Configuration: All alkali metals have one electron in their outermost shell, specifically in the s orbital. This makes them highly reactive as they tend to lose this single electron to achieve a stable noble gas configuration with a complete outer shell.

2. Similar Chemical Properties: Alkali metals share similar chemical properties due to their similar outermost electronic configuration. They readily lose their outermost electron to form positively charged ions (cations) with a charge of +1. This common behavior is a defining characteristic of Group 1 elements.

3. Reactivity Trend: Reactivity increases as you move down Group 1. This trend can be attributed to the decreasing ionization energy down the group, which makes it easier for the outermost electron to be removed. This leads to more vigorous reactions with water and other substances.

4. Similar Physical Properties: Alkali metals exhibit similar physical properties such as softness, low melting points, and low densities. These properties arise from the weak metallic bonding and the tendency for the atoms to form metallic lattices.

In summary, the placement of alkali metals in Group 1 of the periodic table is justified by their similar outermost electronic configuration, resulting in similar chemical properties, reactivity trends, and physical properties, all of which are characteristic of Group 1 elements.