Mnemonic Device:

• Hi, Hello! Little Beryll Brown Cracking Nuts On Friday. Nellie’s Naughty Magpie Always Sings Pop Songs Clearly After Killing Cathy.

Explanation: to remember the first twenty elements of the Periodic Table.

• Hydrogen 1, Helium 2, Lithium 3, Beryllium 4, Boron 5, Carbon 6, Nitrogen 7, Oxygen 8, Fluorine 9, Neon 10, Sodium 11, Magnesium 12, Aluminium 13, Silicon 14, Phosphorus 15, Sulphur 16, Chlorine 17, Argon 18, Potassium 19, Calcium 20