Study the picture of copper. How many connections or bonds does the center atom have to the other atoms?

Its strengthits conductivity of heat and electricity its shiny colourmalleable and ductility

Reducing agents  oxidized by the reaction 

So the main goal for the elements is stability which is a complete/full valence shell and typically the magic number for a stable element is 8 valence electron but not always. so elements to the left of the periodic table tend to be way less stable then those on the right, so the elements on the left are much more reactive.