What is the general trend in atomic size within a group?within a period?
within a period...it decreases
In a group..it increases as atomic number increases.
To understand the general trend in atomic size within a group and within a period, let's first clarify what we mean by these terms.
- A group refers to the vertical columns on the periodic table, also known as families. Elements within the same group share similar chemical properties because they have the same number of valence electrons.
- A period refers to the horizontal rows on the periodic table. Elements within the same period have the same number of energy shells or levels.
Now, let's examine the trend in atomic size within a period and within a group:
1. Atomic size within a period:
As you move from left to right across a period, atomic size generally decreases. This is because the number of protons (nuclear charge) increases, attracting the electrons more strongly towards the nucleus. The increased positive charge pulls the electron cloud closer to the nucleus, resulting in a smaller atomic size.
2. Atomic size within a group:
As you move down a group, atomic size generally increases. This is because new energy shells or levels are added as you go down the group. The additional energy levels shield the outermost electrons from the attractive force of the nucleus. As a result, the electron cloud expands, leading to an increase in atomic size.
In summary, within a period, atomic size decreases from left to right, while within a group, atomic size increases from top to bottom.