A trend is a pattern, a predictable and knowable next step for one concept or another. For example, THE GROUP TREND FOR ATOMIC MASS IS INCREASING. That means when you compare the atomic mass of elements in any (top to bottom) group, the mass increases as you drop box by box towards the bottom of the table.
THE PERIOD TREND FOR ATOMIC MASS IS INCREASING. This is also true, as the masses of the atoms increases going left to right on the table. There are a few glitches, trends are not laws, but generally the masses increase Look at the masses for Cobalt and Nickel now (really, now, get your periodic table now).
That is an exception to the “trend”, which is okay. We can explain that by bringing isotopes into the conversation. If you don’t “get that”, pay attention in class and read the BASICS.
Other trends you should be familiar with are net nuclear charge, atomic size or radius, cation and anion size, electronegativity, first ionization energy, and metallic or nonmetallic properties.
Each of these follows a simple pattern (with some exceptions) going down a group, or across a period.
The Periodic Table is great, look hard at it. The Trends Handout is due on Monday or else it’s late and you are not keeping up with me or the rest of the students. Get going.