Which of the following shows the correct order of Family #1 elements from least to most reactive?

A) Li, Na, Rb, K
B) Li, Na, K, Rb
C) Rb, K, Na, Li
D) Li, Na, K, Ba

reading down the column, they become more reactive.

fdfde

To determine the correct order of reactivity for the elements in Family #1 (also known as Group 1 or alkali metals), we need to analyze their positions in the periodic table.

The alkali metals include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), and Cesium (Cs). The most important factor affecting reactivity within a group is the increase in atomic radius as you go down the periodic table.

In this case, we need to determine the element with the smallest atomic radius, which will be the most reactive, and the element with the largest atomic radius, which will be the least reactive.

Option A) Li, Na, Rb, K
Option B) Li, Na, K, Rb
Option C) Rb, K, Na, Li
Option D) Li, Na, K, Ba

Analyzing the options:

Option A: This option places the elements in increasing order of atomic number. However, the correct order of reactivity should follow the trend of increasing atomic radius, not atomic number.

Option B: This option is incorrect because it places Rubidium (Rb) before Potassium (K), whereas in reality, Rb has a larger atomic radius and should be less reactive.

Option C: This option correctly places Rubidium (Rb) before Potassium (K) and Sodium (Na), indicating an increasing order of atomic radius. However, it incorrectly places Lithium (Li) at the end, which has the smallest atomic radius and should be the most reactive. Therefore, Option C is incorrect.

Option D: This option places Lithium (Li), Sodium (Na), and Potassium (K) in the correct increasing order of atomic radius. However, it introduces Barium (Ba), which is not a member of Group 1. Therefore, Option D is incorrect.

Based on the analysis, the correct answer is Option B) Li, Na, K, Rb. This option correctly arranges the elements in increasing order of atomic radius, which is the same as the order of increasing reactivity for the alkali metals in Family #1.