No. Neon was not known during the time when people seriously practiced alchemy.
The alchemists were unaware that atoms even existed.
The Europeans from the Middle Ages.
(sry for spelling) Chinese alchemists were looking for the secret to immortality for there emperor but they failed every time and the person who failed was sentence to death they be lived that to get to this goal they needed a philoshper stone European alchemists were diff rent thought they did not want immortality they wanted to be able to change rocks,silver,copper,etc in to gold so that they would have an endless supply
They were trying to convert lead into gold.
Some islamic alchemists are: Jabir ibn Hayyan, Al-Tughrai, Khalid ibn Yazid, Abu Bakr al Razi, Ibn Umayl etc.
I don't think "alchemists" is the word you meant to use, because your question does not make sense. Alchemists are people who try to magically turn lead into gold, or otherwise magically turn one substance into another.
It effects this world in no way what so ever because it doesn't exist, alchemists on the other side of the "gateway" use parts of this world for energy to preform alchemy.
neon signs
Cerium was not known by alchemists.
i dont think so.....they were trying for a really long time though
Add neon duct tape, use neon paints or neon markers.
neon lights
The alchemists were unaware that atoms even existed.
Transmutation circles were not used by real-life alchemists. They are a fictional concept popularized in manga/anime such as "Fullmetal Alchemist." Real alchemists focused on practical experiments and symbolic language to convey their ideas, rather than using intricate diagrams.
Most of the strongest Alchemists appear to be men.
It began in the 1600's. Nicolas Flamel was the first person to ever be called an "Alchemist". He was the birth of the term.
You can use them for signs.