Dmitri Mendeleev is known as the father of the periodic table of elements, and rightly so. He ordered the elements correctly based on their properties, which helped predict the discovery of new elements. But he wasn't the first to come up with the idea of periodicity of elements, or the first to try to make a chart.
John Alexander Newlands was a chemist at a sugar company, but felt understimulated. By studying the different elements, he noticed a strange periodicity to their properties. After some manipulation, he even came up with a chart in which elements that shared properties were grouped all in a row.
When he presented this amazing chart to the Chemical Society, he was ridiculed by everyone in attendance. Unfortunately, Newland had chosen to order the elements by mass — the number of protons and neutrons in each atom — rather than by number of protons. Although this worked well enough with the lighter elements, once he got past calcium he had to make alterations on his chart. Sometimes two elements shared the same square on his chart. Sometimes he changed around the order. Sometimes unlike elements were awkwardly grouped together. The attendees at the Chemical Society presentation were unimpressed, and one even suggested that he might as well have listed elements by alphabetical order.
Discouraged, Newlands went back to his day job, only to find that, a few years later, Mendeleev was being hailed for the same idea that got him ridiculed. Mendeleev's chart was more predictive, and more consistent than Newlands' chart, it was true. But Newlands' chart had been used to predict such elements as germanium, and more importantly, the periodicity of the properties of the elements had been Newlands' idea. Sadly, despite strenuous efforts on Newlands' part to be recognized, he was entirely eclipsed. It was only in 1998 that his chart was dusted off and he got some credit for his ideas.