Questions: Place the following elements in order of decreasing atomic size: tellurium, bromine, argon, cesium, strontium, and selenium. Rank from largest to smallest. To rank items as equivalent, overlap them.

Solution Steps

Atomic size generally increases as you move down a group in the periodic table and decreases as you move from left to right across a period. This is due to the addition of electron shells as you move down a group and the increase in effective nuclear charge as you move across a period.

• Cesium (Cs): Group 1, Period 6
• Strontium (Sr): Group 2, Period 5
• Tellurium (Te): Group 16, Period 5
• Selenium (Se): Group 16, Period 4
• Bromine (Br): Group 17, Period 4
• Argon (Ar): Group 18, Period 3

• Cesium (Cs): Largest atomic size because it is in Group 1, Period 6.
• Strontium (Sr): Next largest, in Group 2, Period 5.
• Tellurium (Te): Larger than Se and Br, in Group 16, Period 5.
• Selenium (Se): Larger than Br, in Group 16, Period 4.
• Bromine (Br): Smaller than Se, in Group 17, Period 4.
• Argon (Ar): Smallest atomic size, in Group 18, Period 3.

Final Answer