Electronium

Electronium has the atomic number ¼ and is a soup-like element that is consisted of ¾ electrons and ¼ neutrons. It has a half-life of 33 billion billion billion years and 7 minutes 19 seconds and 50 milliseconds.

Variations
There are 3 variations of Electronium.

The first one is Electronium prime. It is consisted of ¾ electrons and ¼ neutrons.

The second one is named Electronium². It consists of ⅔ electrons, 2/8 neutrons and 1/12 pure quarks. It has a practically infinite half life because quarks don't decay.

The third one is called Electronium³. It is what happens after Electronium² decays. It is composed of the remains of electrons and neutrons. Some scientists argue that this is a completely new element however the claim is disputed.