Elementary

I've done quite a few nature-name posts, but I realized I'd left out a lot of names! Captain Planet would be ashamed.

Earth:

• Avani (ah-vah-NEE)--Hindi, feminine
• Bhumi (bhoo-mee)--Hindi, feminine
• Daichi (dah-ee-chee)--Japanese, masculine; "great earth/land" [other meanings possible dep. on characters]
• Demeter (deh-MEE-ter, deh-MEH-tehr)--Ancient Greek, feminine; "earth mother" 
• Gaia (GAH-yah)--Greek, feminine
• Ila (EE-lah)--Hindi, feminine
• Kun (KOON)--Chinese, usually masculine
• Terra (TEHR-rah)--English [from Latin], feminine

Wind:

• Anemone (ah-NEM-ah-nee)--English [from Greek], feminine
• Anil (an-NEEL), masculine; Anila (ah-NEE-lah), feminine--Hindi
• Era (EH-rah)--Albanian, feminine
• Ghobad (ghoh-BAHD)--Persian, masculine
• Haizea (eye-seh-ah)--Basque, feminine
• Ilma (EEL-mah)--Finnish, feminine; "air"
• Meltem (mel-TEM)--Turkish, feminine; "breeze"
• Nasim (nah-SEEM)--Arabic, feminine; "breeze"
• Tuula (TOO-lah)--Finnish, feminine. Other forms include Tuuli, Tuulia, & Tuulikki (TOO-lik-kee).
• Vayu (VAH-yoo)--Hindi, masculine
• Zephyr (ZEF-er)--Greek, masculine; "west wind". French feminine form is Zéphyrine.

Fire:

• Agni (AHG-nee)--Hindi, masculine
• Aodhán (AY-ahn, AY-dahn), masculine; Aodnait (AY-nat), feminine--Irish, "little fire". Anglicized as Aidan & Enat, respectively.
• Azar (ah-ZAR)--Persian, feminine
• Cináed (KIN-ee, KIN-ay, KIN-ahd)--Scottish, masculine; "born of fire". Anglicized as Kenneth.
• Fiammetta (fee-ah-MEH-tah)--Italian, feminine; "little fire"
• Jehoash (jeh-HOH-ash)--English [from Hebrew], masculine; "fire of God". Another form is Joash (JOH-ash).
• Nina (NEE-nah)--Quechua, feminine
• Plamen (PLAH-men)--Slavic, masculine
• Shula (SHOO-lah)--Arabic, feminine
• Şule (shoo-LEH)--Turkish, feminine
• Ugnė (OOG-nee)--Lithuanian, feminine

Water:

• Aysu (eye-SOO)--Turkish, feminine; "moon & water"
• Damla (dahm-LAH)--Turkish, feminine; "water droplet"
• Douglas (DUG-las)--Scottish, masculine; "dark water"
• Kelda (KEL-dah)--English [from Old Norse], feminine, "spring, fountain"
• Maayan (mah-ah-yahn)--Hebrew, feminine; "spring, fountain"
• Mayim (mah-yeem)--Hebrew, feminine. Another form is Maya.
• Mortimer (MOR-tim-er)--English [from Old French], masculine; "still water"
• Neith (NEETH, NAYTH)--English [from ancient Egyptian], feminine
• Nerio (NEHR-yoh)--Italian [from Greek], masculine
• Shui (shoo-ee)--Chinese, usually masculine
• Su (SOO)--Turkish, feminine
• Tirto (TEER-toh)--Javanese, masculine; "holy water"