Here's why:
* French nouns have genders. Unlike English, French nouns are either masculine or feminine.
* The ending often determines gender. While there are exceptions, words ending in "-e" are usually feminine.
* "Allemagne" follows this rule. It ends in "-e" and is therefore feminine.
This means you would use the feminine articles "la" or "une" before "Allemagne" depending on the context:
* "La" is the definite article (the) for feminine singular nouns.
* "Une" is the indefinite article (a/an) for feminine singular nouns.