manganese magnesium
ytterbium yttrium
erbium terbium ytterbium
copper copernicium
thallium thulium thorium
zinc zirconium
lutetium ruthenium
boron bohrium
titanium tin
rhodium rhenium
niobium nihonium
niobium nobelium
iron fermium
potassium calcium gallium
sodium nitrogen
platinum silver
lead molybdenum
krypton lanthanum
barium tungsten
francium gallium lutetium
ruthenium moscovium
germanium rhenium
chromium iridium
bromine osmium
radon radium actinium
caesium indium
zirconium gold
antimony tin
neptunium nihonium
actinium acetyl/acetate (latter not an element)
americium ammonium (latter not an element)
indium iminium (latter not an element)
(The reasons for the similarity between some of these might be so obscure as to be considered puzzles.)
EmoticonEmoticon