Question

Arrange the following elements in order of increasing (from smallest to largest) atomic size: K, O, Cs, Se. Explain the reasoning behind your chosen order. Do not simply restate the trend, but rather explain why the trend exists.

Answer 1

In order of increasing atomic size: O, Se, K, Cs. Atomic size increases from top to bottom and decreases from left to right in the periodic table.

Step-by-step explanation:

The elements can be arranged in order of increasing atomic size as follows:

O

1. Se
2. K
3. Cs

The reasoning behind this order is based on the periodic trend of atomic sizes. Atomic size generally increases from top to bottom in a group and decreases from left to right in a period.

In this case, oxygen (O) has the smallest atomic size because it is located at the top of Group 16 (the oxygen family) and has the highest effective nuclear charge. Selenium (Se) comes next because it is below oxygen in the same group and has an additional electron shell, making it larger. Potassium (K) is larger than both oxygen and selenium because it is located in Group 1 (the alkali metals) and has an extra electron shell. Cesium (Cs) is the largest because it is located below potassium and has even more electron shells.

Answer 2

They’re going to increase in atomic size based on how many electrons they have. You should be able to look at a periodic table or just look up how many electrons each of them has and then you can put it in that order