<Tr> <Td> 18 </Td> <Td> Ar </Td> <Td> Argon </Td> <Td> the Greek argos,' idle' </Td> <Td> 18 </Td> <Td> </Td> <Td> 39.948 (1) </Td> <Td> 0.0017837 </Td> <Td> 83.80 </Td> <Td> 87.30 </Td> <Td> 0.52 </Td> <Td>--</Td> <Td> 3.5 </Td> </Tr> <Tr> <Td> 19 </Td> <Td> </Td> <Td> Potassium </Td> <Td> New Latin potassa,' potash' (kalium in Latin) </Td> <Td> </Td> <Td> </Td> <Td> 39.0983 (1) </Td> <Td> 0.862 </Td> <Td> 336.53 </Td> <Td> 1032 </Td> <Td> 0.757 </Td> <Td> 0.82 </Td> <Td> 20900 </Td> </Tr> <Tr> <Td> 20 </Td> <Td> Ca </Td> <Td> Calcium </Td> <Td> the Latin calx,' lime' </Td> <Td> </Td> <Td> </Td> <Td> 40.078 (4) </Td> <Td> 1.54 </Td> <Td> 1115 </Td> <Td> 1757 </Td> <Td> 0.647 </Td> <Td> </Td> <Td> 41500 </Td> </Tr> <Tr> <Td> 21 </Td> <Td> Sc </Td> <Td> Scandium </Td> <Td> Scandia, the Latin name for Scandinavia </Td> <Td> </Td> <Td> </Td> <Td> 44.955908 (5) </Td> <Td> 2.989 </Td> <Td> 1814 </Td> <Td> 3109 </Td> <Td> 0.568 </Td> <Td> 1.36 </Td> <Td> 22 </Td> </Tr>

Name of real chemical element in the periodic table