Question: what are periodic trends?

Fiona Fotherby answered on 1 Apr 2022:

That’s are great question! The periodic table is arranged cleverly in a way that supports the interesting chemical properties and trends in the elements. As you may know, each element has its own atomic number, which is the number of protons in its nucleus. This is the unique property that makes up each element.
When looking at the periodic table, theres is a trend in increasing size of atomic radius, that means the size of the elements increase, when we go from top of the table (Helium- smaller) to Bottom (Francium- bigger) . Also, the atomic radius increases from right to left across row (Fluorine is the smallest in the row, and Lithium is largest).
Atomic radius is related to an elements electronegativity. The more electronegative atom, meaning it likes to hold its negative charge, holds it’s negative charge more closely. This makes the atom smaller! This is why Flourine is the smallest. It likes to be the most negative and hold its electrons very tight and close, making it smaller. Other bigger atoms give their electrons more freely. They are like big electron clouds, and they are happy to give up their electrons more easily , which makes them larger (lower electron affinity and lower ionisation potential). I hope this helps! Stay curious!