Silver was written about in 900BC in India, though we do not know who discovered or when Silver. Silver has been in use as far back as 3400BC in Egyptian objects. Silver has the ability to halt bacteria and fungi growth. This is why Silver can be found in wound dressings. (Due to the fact that there is no date of discovery, I used the date since the element was in use.)
It is unsure when or who discovered Mercury, but it was in use since 1500BC by the Chinese, Egyptians and Hindus. Chinese Emperors once used Mercury in medicine to prolongate their lives but we now know that Mercury probably shortened the Emperor's life due to Mercury's toxins that may severely harm people. (Due to the fact that there is no date of discovery, I used the date since the element was in use.)
Arsenic is said to be discovered as a unique element by Geber (an alchemist) in 800BC. Geber recorded how to prepare Arsenic in "Liber Fornacum". Many accredit this discovery to Albertus Magnus who found Arsenic in 1250BC. Arsenic is utilised in modern animal feeds to stimulate growth and prevent disease.
Phosphorus was discovered in 1 by German alchemist, Henning Brand. Brand stumbled upon Phosphorus when trying the create 'the Philosopher's Stone'. Whilst experimenting with urine Brand managed to separate a white glowing material which happened to be Phosphorus. Phosphorus is part of DNA, RNA, and ATP, this means every living cell requires and has Phosphorus.
A Swedish chemist by the name of Georg Brandt, was the first person to successfully isolate Cobalt, which was done in 1735 ad. Cobalt was in use since 400 bc by the Egyptians in sculptures. Cobalt is known for the magnificent blue colour it stains glass, ceramic and glazes with. Cobalt is able to withstand enormous temperatures, it becomes solid at room temperature and doesn't melt til 1495 degrees Celsius.
Paracelsus (1500's ad) and Robert Boyle (1671 ad) had both discovered Hydrogen but hadn't followed up on their discoveries. Therefore Henry Cavendish is accredited for the discovery of Hydrogen. Henry also proved that water wasn't made up of one element, by burning the Hydrogen. Hydrogen can be found in the sun and all other stars, in fact Jupiter the planet is mostly consistent of Hydrogen. It is thought that Hydrogen is the most abundant element in universe.
Carl Wilhelm Scheele a Swedish chemist was the first person to isolate Chlorine gas and he continued to study Chlorine. Around 900 ad a Persian alchemist created a form of Chlorine called Hydrochloric acid, which combined with nitric was used to dissolve gold around 1200 ad. Despite its prior discovery Chlorine was regarded as a unique element until 1810 by Sir Humphry Davy.
Discovered by two Swedish brothers who were both chemist, Juan Jose and Fausto Elhuyar in 1783. It was discovered when the brothers were analyzing samples of the mineral wolframite. They succeeded in isolating the tungsten from wolframite by reducing the acid to charcoal. Tungsten to this day is extract using the same method the two brothers who discovered it used, from wolframite and scheelite.
Martin Heinrich Klaproth isolated the Uranium oxide in 1789 and he had mistaken it for a new element. Only in 1841 ad had the metal Uranium get isolated, which was done by Eugene-Melchior Peligot. Uranium oxide used to be used as yellow pigment in ceramic glazes in early 79 ad.
Sir Humphry Davy, Joseph Louis Gay-Lussac and Louis Jacques Thenard reacted boric acid with potassium and ended up isolating a new element, Boron which Davy originally named Boracium. Boron acid is sometimes found in volcanic spring waters, and isn't toxic to mammals.
Calcium discovered by Sir Humphry Davy a British chemist in 1808 through electrolysis (direct electric current to cause a reaction that otherwise wouldn't occur) of lime and mercuric oxide. Calcium is always found as a part of several minerals, and is the fifth most abundant element in our Earth's crust, making it essential to life.
Hans Christian Orsted first isolated and produced Aluminum as a metal in 1825 by reacting Aluminum Chloride with Potassium Amalgam. Before Orsted discovered Aluminum metal, ancient Greeks and Romans used Aluminum salts to dress wounds and was considered to be more precious than Gold! Aluminum is extremely reactive resulting in Aluminum never being found uncombined in nature.
Bromine was discovered when Carl Jacob isolated Bromine from spring waters in his hometown. He saturated a solution of the mineral using chlorine and used an ether for the extraction of the Bromine. Others say that Antoine Ballard discovered Bromine in 1826 ad since Jacob published his findings a long time after he found them. Ballard extracted Bromine from seaweed, by reacting seaweed ash with chlorine.
Helium was sited by a French astronomer Pierre Janssen while observing the solar eclipse in 1868 ad. Helium wasn't isolated til 1895 by Sir William Ramsay. Ramsay treated mineral cleveite with mineral acids, when he analysed the mixture, Ramsay discovered a yellow line in the emission spectrum (a band of colours).This yellow line was Helium. Helium is lighter than air and is the second most abundant element in the universe.
Radium was discovered by Marie Sklodowska Curie a Polish chemist and French chemist Pierre Curie in 1898. Marie Curie discovered Radium from a pitchblende. Marie extracted the Uranium from the Pitchblende but then noticed the Pitchblende still contained some kind of strong radioactive element. Maria Curie refined several tons of pitchblende to extract only tiny amounts of radium and polonium ( another radioactive element Curie discovered). Radium is around one million times more radioactive the Uranium. Radium is so radioactive that Curie's notebooks are far too radioactive to be handled safetly to this day.
X-ray spectroscopy was used to discover Hafnium in 1923 by Danish chemist Dirk Coster and Hungarian chemist Charles de Hevesy. X-ray spectroscopy was used to study the arrangement of the electrons on the outer shell of zirconium. The task of isolating the Hafnium is a hard one, since Hafnium is in every ore of zirconium. Hafnium is used in the control rods (regulate heat to insure center doesn't melt down) of nuclear reactors since it is a good absorber of neutrons..
Rhenium was discovered by German chemists Ida Tacke-Noddack, Walter Noddack, and Otto Carl Berg. This group detected Rhenium spectroscopically in platinum ores and in the minerals columbite, gadolinite and molybdenite. Nowadays Rhenium isolated as a byproduct of refining molybdenum and copper.
Einsteinium was discovered by a group of scientists lead by Albert Ghiorso as they were studying the radioactive debris from the first detonated hydrogen bomb. Einsteinium was discovered by combining 15 neutrons with Uranium. Einsteinium requires a long process and can only be made in small quantities so Einsteinium is only used for scientific purposes.