What are the trends that you can identify whenever elements are arranged based on increasing atomic numbers?

Answer 1

Reactivity, density, hardness, colour, malleabilty etc.

Answer 2

effective nuclear charge decrease
atomic radii size increase
electron affinity/ ionization energy increase
acidity increase (a hydrogen is connected to the elements)
weight increase
increase in electrons, protons, and neutrons (in general)
Other trends rely on other information as well

Metallic character and Reactivity arent periodic trends even He can be metallic! Density and electronegativity are periodic trends but not with increasing atomic number. Color is not really a periodic trend at all. Through there are some spectroscopic and band gap trends which lead to color trends.

Answer 3

increasing or decreasing atomic radius, ionic radius,electron affinity, electro negativity,metallic character, reactivity,etc., along rows and groups..... beside these we have lot of similarities among the elements in same group etc...