Question

1. rank the following elements by decreasing atomic radius: barium, mercury, tungsten, polonium mercury, polonium, tungsten,barium

Explanation:

Step1: Recall atomic - radius trend

Atomic radius decreases across a period and increases down a group in the periodic table. Barium is in Group 2 and Period 6. Tungsten is in Group 6 and Period 6. Polonium is in Group 16 and Period 6. Mercury is in Group 12 and Period 6.

Step2: Compare elements in the same period

Since they are all in Period 6, as we move from left - to - right across the period, the effective nuclear charge increases, pulling the electrons closer to the nucleus and decreasing the atomic radius. Barium is the left - most among them, so it has the largest atomic radius. Then comes tungsten, followed by polonium, and mercury has the smallest atomic radius among these four elements in Period 6.

Answer:

Barium, Tungsten, Polonium, Mercury