Given what you're trying to achieve, new elements aren't going to help you. I'm not an organic chemist, but what I do know about organic chemistry is that the effect you're trying to achieve is almost always solved with a compound, not an element.

Caffeine (C8 H10 N4 O2); a carbo-hydro-nitrate (?) gives us a lift and makes us feel more energetic because it mimics a chemical in the brain that is generated when we're tired. The receptors for that chemical in the brain receive enough of that chemical, and it tells our brain 'we're tired'. We go to sleep, the chemical breaks down and our brain is no longer receiving the tired signal.

What Caffeine does is block the receptors, without triggering the response. As such, it actually blocks the real chemical from being received by the brain so it doesn't get the signal being generated chemically.

(This is all a simplification, but functionally correct)

The point being, that exotic elements aren't that common in drugs that affect the brain. Check out Alcohol (C2H6O), LSD (C20H25N3O), Cocaine (C17H21NO4), Methamphetamine (C10H15N), and even Anti-dpressants.

What do all of these seem to have in common? They're all Carbon, Hydrogen, Nitrogen and Oxygen combined in some permutation.

Ultimately, there's good reasons for this. These are the chemical elements that have been built into life for billions of years, and the sequencing of compounds allow for far more flexibility than a rare element.

I really think that your best bet for believability is that your secret element isn't on the Periodic Table, it's a CHNO compound that excites a specific part of the brain to over-activity, opening up a latent capability that humans would have naturally evolved in the next 500k years or so. It's certainly more scientifically more likely than a rare element combining with existing stable organic molecules to generate new classes of compounds to somehow augment a stable biological chemical code base.

But, that last statement is only personal opinion.

Given what you're trying to achieve, new elements aren't going to help you. I'm not an organic chemist, but what I do know about organic chemistry is that the effect you're trying to achieve is almost always solved with a compound, not an element.

Caffeine (C₈H₁₀N₄O₂); a carbo-hydro-nitrate (?) gives us a lift and makes us feel more energetic because it mimics a chemical in the brain that is generated when we're tired. The receptors for that chemical in the brain receive enough of that chemical, and it tells our brain 'we're tired'. We go to sleep, the chemical breaks down and our brain is no longer receiving the tired signal.

What Caffeine does is block the receptors, without triggering the response. As such, it actually blocks the real chemical from being received by the brain so it doesn't get the signal being generated chemically.

(This is all a simplification, but functionally correct)

The point being, that exotic elements aren't that common in drugs that affect the brain. Check out Alcohol (C₂H₆O), LSD (C₂₀H₂₅N₃O), Cocaine (C₁₇H₂₁NO₄), Methamphetamine (C₁₀H₁₅N), and even Anti-depressants.

What do all of these seem to have in common? They're all Carbon, Hydrogen, Nitrogen and Oxygen combined in some permutation.

Ultimately, there's good reasons for this. These are the chemical elements that have been built into life for billions of years, and the sequencing of compounds allow for far more flexibility than a rare element.

I really think that your best bet for believability is that your secret element isn't on the Periodic Table, it's a CHNO compound that excites a specific part of the brain to over-activity, opening up a latent capability that humans would have naturally evolved in the next 500k years or so. It's certainly more scientifically more likely than a rare element combining with existing stable organic molecules to generate new classes of compounds to somehow augment a stable biological chemical code base.

But, that last statement is only personal opinion.