What result came of more chemically similar lanthanide elements being discovered ?
In presentations of the periodic table , the lanthanides and the actinides are customarily shown as two additional rows below the main body of the table , with placeholders or else a selected single element of each series ( either lanthanum and actinium , or lutetium and lawrencium ) shown in a single cell of the main table , between barium and hafnium , and radium and rutherfordium , respectively .