Chemical element
An oxygen atom contains exactly eight protons in its nucleus. This count defines the element as oxygen, regardless of how many neutrons surround those protons. Scientists call this proton count the atomic number. Atoms with six protons are always carbon. Atoms with seventy-nine protons are always gold. Changing the proton count transforms one element into another through nuclear reactions. Isotopes exist when atoms share a proton count but differ in neutron numbers. Carbon-12 has six neutrons while carbon-14 carries eight neutrons. Both remain carbon because their proton count stays at six. The International Union of Pure and Applied Chemistry recognized 118 elements by November 2016. The first 94 occur naturally on Earth. The remaining 24 are synthetic elements created in laboratories.
Plato wrote about four classical elements around 360 BCE in his dialogue Timaeus. He described fire as tetrahedrons and water as icosahedrons. Robert Boyle published The Sceptical Chymist in 1661 to challenge ancient definitions. Antoine Lavoisier listed 33 elements in his 1789 book Elements of Chemistry. Dmitri Mendeleev arranged 63 known elements into rows and columns in 1869. His periodic table predicted properties for undiscovered substances. Henry Moseley discovered that atomic number, not atomic weight, defines an element in 1913. Marguerite Perey isolated francium in 1939 as the final naturally occurring radioactive element. Glenn T. Seaborg pioneered work creating transuranic elements after 1940. By January 2016, IUPAC confirmed all 118 elements had been discovered.
Dmitri Mendeleev organized elements by increasing atomic number into periods and groups. Each row represents a period where atoms share electron shell counts. Columns group elements with recurring chemical properties. Oxygen sits in group 16 while gold occupies group 11. Metals conduct electricity whereas nonmetals generally do not. Bromine and mercury remain liquid at zero degrees Celsius. Gallium melts at approximately thirty degrees Celsius but boils near two thousand four hundred degrees. Carbon exists as diamond or graphite depending on pressure conditions. Silicon forms cubic crystals under high pressure inside planetary interiors. The periodic table contains eighteen numbered groups. Tin holds ten stable isotopes more than any other single element. Elements from one to eighty-two possess at least one stable isotope except technetium and promethium.
Hydrogen-1 and helium-4 formed during Big Bang nucleosynthesis within the first twenty minutes of the universe. Lithium and beryllium appeared only in tiny traces during that initial expansion. Stars fuse hydrogen into helium to generate energy for billions of years. Massive stars create elements up to iron through alpha processes. Iron-56 represents the most stable nuclide produced from fourteen helium nuclei. Supernovae explode to forge heavy elements like uranium and plutonium via neutron capture. Neutron star mergers also produce these heavy transuranic materials. Cosmic rays fragment carbon, nitrogen, and oxygen atoms to form lithium, beryllium, and boron. Carbon-14 continuously forms in Earth's atmosphere when cosmic rays impact nitrogen atoms. Argon-40 results from potassium-40 decay over geological time scales. Hydrogen comprises seventy-five percent of primordial matter by mass while helium accounts for twenty-five percent.
Hennig Brand discovered phosphorus in 1669 as the first recorded new element. Henri Becquerel found radioactivity in uranium in 1896. Glenn T. Seaborg synthesized plutonium in 1940 using nuclear reactors. The Flerov Laboratory of Nuclear Reactions created oganesson on the 9th of October 2006 in Dubna Russia. Tennessine was claimed as discovered in 2009 before official recognition. IUPAC officially named four newest elements with atomic numbers 113, 115, 117, and 118 on the 28th of November 2016. Scientists have produced more than one thousand different isotopes through nuclear transmutation. Nine hundred of these isotopes do not appear naturally anywhere on Earth. Transuranic elements beyond plutonium possess half-lives too short to survive since Earth formed. Americium through einsteinium were detected in the spectrum of Przybylski's star. These heavy elements exist only because humans force nuclei together in particle accelerators or reactors.
Carbon-12 has six protons and six neutrons while carbon-14 carries eight neutrons. Tritium undergoes beta decay with a half-life of twelve point three years. Bismuth-209 exhibits an alpha decay half-life exceeding two billion years. Tellurium-128 transmutes through double beta decay over twenty-two point five times ten to the power of twenty-four years. Most stable elements contain multiple isotopes averaging three point one per element. Only twenty-six elements remain monoisotopic with exactly one stable isotope. Tantalum-180m exists as metastable despite having observationally stable counterparts. Lead requires approximately three neutrons for every two protons to maintain stability. Radioactive decay transforms unstable nuclei into other elements via alpha, beta, or spontaneous fission processes. The human body receives radiation exposure primarily from carbon-14 and potassium-40 intake. Scientists define stability when isotopes possess lifetimes longer than ten seconds required to form electronic clouds.
Continue Browsing
Common questions
What defines the element oxygen?
An oxygen atom contains exactly eight protons in its nucleus. This count defines the element as oxygen regardless of how many neutrons surround those protons.
When did scientists recognize 118 elements by November 2016?
The International Union of Pure and Applied Chemistry recognized 118 elements by November 2016. The first 94 occur naturally on Earth while the remaining 24 are synthetic elements created in laboratories.
Who discovered phosphorus in 1669 as the first recorded new element?
Hennig Brand discovered phosphorus in 1669 as the first recorded new element. Scientists have produced more than one thousand different isotopes through nuclear transmutation since that time.
How do stars create elements up to iron through alpha processes?
Massive stars create elements up to iron through alpha processes during their life cycles. Iron-56 represents the most stable nuclide produced from fourteen helium nuclei before supernovae explode to forge heavy elements like uranium and plutonium via neutron capture.
On what date was oganesson created in Dubna Russia?
The Flerov Laboratory of Nuclear Reactions created oganesson on the 9th of October 2006 in Dubna Russia. IUPAC officially named four newest elements with atomic numbers 113, 115, 117, and 118 on the 28th of November 2016.