This is a soft keyboard that is convenient for writing chemical equation.
Alphabets for element symbol, numbers, superscript, subscript and symbols for chemical equation can be entered without switching the keyboard or converting.

You can enter alphabets "A,B,C,E,F,G,H,I,K,L,M,N,O,P,S,U,Z" for element symbols, numbers "0,1,2,3,4,5,6,7,8,9", superscript "⁰,¹,²,³,⁴,⁵,⁶,⁷,⁸,⁹,⁺,⁻", subscript "₀,₁,₂,₃,₄,₅,₆,₇,₈,₉,ₓ", and "+,→,⇄,↑,↓,(,),[,]" for chemical equation symbols.

Pressing the number continuously changes the subscript number and superscript number.
If you press the key of the alphabet continuously, it switches from uppercase letters to lowercase letters.
If you press the "()" key continuously, it switches to "[]".

Please be aware that superscript, subscript and ⇄ may not be saved properly depending on the character code of the text file to be entered.
If it is UTF-8 of the standard character code of Android OS it can be saved correctly.
There is a possibility of garbled characters when saving with the standard character code of Windows PC.

Element symbol that can be entered
H - Hydrogen
He - Helium
Li - Lithium
Be - Beryllium
B - Boron
C - Carbon
N - Nitrogen
O - Oxygen
F - Fluorine
Ne - Neon
Na - Sodium
Mg - Magnesium
Al - Aluminium
Si - Silicon
P - Phosphorus
S - Sulfur
Cl - Chlorine
K - Potassium
Ca - Calcium
Sc - Scandium
Mn - Manganese
Fe - Iron
Co - Cobalt
Ni - Nickel
Cu - Copper
Zn - Zinc
Ga - Gallium
Ge - Germanium
As - Arsenic
Se - Selenium
Nb - Niobium
Mo - Molybdenum
Ag - Silver
In - Indium
Sn - Tin
Sb - Antimony
I - Iodine
Cs - Caesium
Ba - Barium
La - Lanthanum
Ce - Cerium
Pm - Promethium
Sm - Samarium
Eu - Europium
Ho - Holmium
Lu - Lutetium
Hf - Hafnium
Os - Osmium
Au - Gold
Hg - Mercury
Pb - Lead
Bi - Bismuth
Po - Polonium
Ac - Actinium
Pa - Protactinium
U - Uranium
Np - Neptunium
Pu - Plutonium
Am - Americium
Cm - Curium
Bk - Berkelium
Cf - Californium
Es - Einsteinium
Fm - Fermium
No - Nobelium
Sg - Seaborgium
Bh - Bohrium
Hs - Hassium
Cn - Copernicium
Nh - Japanium
Fl - Flerovium
Mc - Moscovium
Og - Oganesson

Element symbols that cannot be entered
Ar - Argon
Ti - Titanium
V - Vanadium
Cr - Chromium
Br - Bromine
Kr - Krypton
Rb - Rubidium
Sr - Strontium
Y - Yttrium
Zr - Zirconium
Tc - Technetium
Ru - Ruthenium
Rh - Rhodium
Pd - Palladium
Cd - Cadmium
Te - Tellurium
Xe - Xenon
Pr - Praseodymium
Nd - Neodymium
Gd - Gadolinium
Tb - Terbium
Dy - Dysprosium
Er - Erbium
Tm - Thulium
Yb - Ytterbium
Ta - Tantalum
W - Tungsten
Re - Rhenium
Ir - Iridium
Pt - Platinum
Tl - Thallium
At - Astatine
Rn - Radon
Fr - Francium
Ra - Radium
Th - Thorium
Md - Mendelevium
Lr - Lawrencium
Rf - Rutherfordium
Db - Dobnium
Mt - Meitnerium
Ds - Darmstadtium
Rg - Roentgenium
Lv - Livermorium
Ts - Tennessine

Enabling Keyboards

01
Go to Settings > System > Languages & input > and tap Virtual keyboard in the Keyboard & inputs section.

02
You'll see a list of each keyboard you've installed.
Tap "Manage keyboards".

03
Toggle on the new keyboard.
You might see a warning that this input method may collect the text you type including personal information.
But this app does not collect any input content.
This is not a warning specific to this application, it will always be displayed if you select a character input application other than the keyboard that is standard on the device.
If you're satisfied with the explanation, tap OK.

Note: Instructions will vary depending on your Android OS.

Switching Keyboards

01
Launch the app you want to type in.

02
Tap to bring up the keyboard.

03
Tap the keyboard icon on the bottom right.
(On some devices this icon isn't present, in that case pull down the notification bar when a keyboard is active.)

04
Choose the keyboard from the list that pops up.

Chemical equation keyboard B