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hexagonal close-packed (hcp) Category: Helium. Helium (from Greek: ἥλιος, romanized: helios, lit. 'sun') is a chemical element; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table.
The number indicates the degree of oxidation of each element caused by molecular bonding. In ionic molecules, the oxidation numbers are the same as the element's ionic charge. Thus for KCl, potassium is assigned +1 and chlorine is assigned -1. [4] The complete set of rules for assigning oxidation numbers are discussed in the following sections.
Element Negative states Positive states Group Notes −5 −4 −3 −2 −1 0 +1 +2 +3 +4 +5 +6 +7 +8 +9 Z; 1 hydrogen: H −1: 0 +1: 1 [1]2 helium: He 0
Helium: Lithium: Beryllium: ... xenon atom in the oxidation state of ... universe decrease as their atomic numbers increase. Helium is the most common element in ...
Group (periodic table) In the periodic table of the elements, each column is a group. In chemistry, a group (also known as a family) [ 1 ] is a column of elements in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table; the 14 f-block columns, between groups 2 and 3, are not numbered.
Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with two neutrons, depending on the isotope, held together by the strong force. Unlike for hydrogen, a closed-form solution to the Schrödinger equation for the helium atom has not been found.
Hydrogen and helium are most common, ... For a given odd mass number, ... 85 Rubidium can form Rb 6 O and Rb 9 O 2 (copper-coloured) upon oxidation in air, ...
Each distinct atomic number therefore corresponds to a class of atom: these classes are called the chemical elements. [5] The chemical elements are what the periodic table classifies and organizes. Hydrogen is the element with atomic number 1; helium, atomic number 2; lithium, atomic number 3; and so on.