Peter Norvig
March 2020

# Elemental Spelling Here's a problem: > Given a word, decide if it can be spelled using only the symbols in the **[periodic table](https://en.wikipedia.org/wiki/Periodic_table)** of elements. For example, the word "bananas" can be spelled with "BaNaNaS" (Barium-Sodium-Sodium-Sulfur). Note that there can be multiple possible spellings for a word—"coin" could be "CoIn" (Cobalt-Indium) or "COIN" (Carbon-Oxygen-Iodine-Nitrogen). Here is a sketch of a recursive algorithm to solve the problem. A word is **spellable** if any of the following are true: - The word is the empty word. - The first 2 letters of the word (capitalized) form an element symbol, and the rest of the word is spellable. - The first 1 letter of the word (capitalized) forms an element symbol, and the rest of the word is spellable. The input to `spellable` should be a string and the output is a boolean. Here is the code: