Upper trigram
☳
Thunder · Zhen
Arousal and shock.
FamilyEldest son
ElementWood
Hexagram 62 of 64
☳☶ Small Exceeding
Attend to small things, not large ones.
Lower trigram
☶
Mountain · Gen
Stillness and limit.
FamilyYoungest son
ElementEarth
The image
Thunder above, Mountain below.
Thunder over Mountain: arousal and shock meeting stillness and limit.
That combination is the whole meaning of hexagram 62. Nothing about it is arbitrary — change either trigram and you get a different hexagram with a different reading, which is why the 64 form a system rather than a list.