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  2. Gallium - Wikipedia

    en.wikipedia.org/wiki/Gallium

    Gallium is a chemical element; it has the symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, [11] gallium is in group 13 of the periodic table and is similar to the other metals of the group (aluminium, indium, and thallium). Elemental gallium is a relatively soft, silvery metal at ...

  3. d-block contraction - Wikipedia

    en.wikipedia.org/wiki/D-block_contraction

    The d-block contraction (sometimes called scandide contraction[1]) is a term used in chemistry to describe the effect of having full d orbitals on the period 4 elements. The elements in question are gallium, germanium, arsenic, selenium, bromine, and krypton [citation needed]. Their electronic configurations include completely filled d orbitals ...

  4. Effective nuclear charge - Wikipedia

    en.wikipedia.org/wiki/Effective_nuclear_charge

    Description. The effective atomic number Z eff, (sometimes referred to as the effective nuclear charge) of an atom is the number of protons that an electron in the element effectively 'sees' due to screening by inner-shell electrons. It is a measure of the electrostatic interaction between the negatively charged electrons and positively charged ...

  5. Electron shell - Wikipedia

    en.wikipedia.org/wiki/Electron_shell

    Electron shell. In chemistry and atomic physics, an electron shell may be thought of as an orbit that electrons follow around an atom 's nucleus. The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 shell" (or "L shell"), then the "3 shell" (or "M shell"), and so on further and further from ...

  6. Germanium - Wikipedia

    en.wikipedia.org/wiki/Germanium

    Germanium is a chemical element; it has symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid (more rarely considered a metal) in the carbon group that is chemically similar to its group neighbors silicon and tin. Like silicon, germanium naturally reacts and forms ...

  7. Isotopes of germanium - Wikipedia

    en.wikipedia.org/wiki/Isotopes_of_germanium

    Germanium (32 Ge) has five naturally occurring isotopes, 70 Ge, 72 Ge, 73 Ge, 74 Ge, and 76 Ge. Of these, 76 Ge is very slightly radioactive, decaying by double beta decay with a half-life of 1.78 × 10 21 years [4] (130 billion times the age of the universe). Stable 74 Ge is the most common isotope, having a natural abundance of approximately ...

  8. Valence electron - Wikipedia

    en.wikipedia.org/wiki/Valence_electron

    In chemistry and physics, valence electrons are electrons in the outermost shell of an atom, and that can participate in the formation of a chemical bond if the outermost shell is not closed. In a single covalent bond, a shared pair forms with both atoms in the bond each contributing one valence electron. The presence of valence electrons can ...

  9. Post-transition metal - Wikipedia

    en.wikipedia.org/wiki/Post-transition_metal

    The peculiar metals occur towards the ends of the rows of the periodic table and include 'approximately:' gallium, indium, and thallium; carbon, silicon '(both of which have some metallic properties, though we have previously treated them as nonmetals),' germanium and tin; arsenic, antimony, and bismuth; and selenium '(which is partly metallic ...