what is the 1st element in the periodic table
Periodic table All elements ranging from atomic numbers 1 (hydrogen) to 118 (oganesson) have been either discovered or synthesized, completing the first seven rows of the periodic table.[1][2] The first 98 elements exist naturally, although some are found only in trace amounts and were synthesized in laboratories before being found in nature.[n 1] Atomic numbers for elements 99 to 118 have only been synthesized in laboratories or nuclear reactors.[3] The synthesis of elements having higher atomic numbers is currently being pursued: these elements would begin an eighth row, and theoretical work has been done to suggest possible appearances for this extension. Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories.
Isotope Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table.
Helium Helium (from Greek: ἥλιος, translit. Helios, lit. 'Sun') is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements.
Isotope The number of protons within the atom's nucleus is called atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.