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  2. Valence issue - Wikipedia

    en.wikipedia.org/wiki/Valence_issue

    Position issues are an alternative to valence issues, as position issues create disagreement among voters because a broad consensus on the issue is lacking. [20] Since position issues are divisive issues they consequently separate potential voters into distinct voting blocs that may support or oppose a way of dealing with the position issue at hand. [21]

  3. List of unsolved problems in biology - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Developmental psychobiology posed this question since the lack of knowledge about the precise coordination of all cells, even those not related anatomically, in space and time during the embryonic period does not allow us to understand what forces at the cellular level coordinate four very general classes of tissue deformation, namely: tissue ...

  4. List of unsolved problems in chemistry - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    In 2020, it was announced that Google's AlphaFold, a neural network based on DeepMind artificial intelligence, is capable of predicting a protein's final shape based solely on its amino-acid chain with an accuracy of around 90% on a test sample of proteins used by the team.

  5. Pnictogen - Wikipedia

    en.wikipedia.org/wiki/Pnictogen

    For example, N 2, the diatomic form of nitrogen, is used as an inert gas in situations where using argon or another noble gas would be too expensive. Formation of multiple bonds is facilitated by their five valence electrons , as the octet rule permits a pnictogen to accept three electrons on covalent bonding.

  6. Valence (chemistry) - Wikipedia

    en.wikipedia.org/wiki/Valence_(chemistry)

    The valence is the combining capacity of an atom of a given element, determined by the number of hydrogen atoms that it combines with. In methane, carbon has a valence of 4; in ammonia, nitrogen has a valence of 3; in water, oxygen has a valence of 2; and in hydrogen chloride, chlorine has a valence of 1.

  7. Orbital hybridisation - Wikipedia

    en.wikipedia.org/wiki/Orbital_hybridisation

    In chemistry, orbital hybridisation (or hybridization) is the concept of mixing atomic orbitals to form new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory. For example, in a carbon atom which forms four single bonds ...

  8. VSEPR theory - Wikipedia

    en.wikipedia.org/wiki/VSEPR_theory

    The steric number of a central atom in a molecule is the number of atoms bonded to that central atom, called its coordination number, plus the number of lone pairs of valence electrons on the central atom. [11] In the molecule SF 4, for example, the central sulfur atom has four ligands; the coordination number of sulfur is four. In addition to ...

  9. Molecule - Wikipedia

    en.wikipedia.org/wiki/Molecule

    For example, water is always composed of a 2:1 ratio of hydrogen to oxygen atoms, and ethanol (ethyl alcohol) is always composed of carbon, hydrogen, and oxygen in a 2:6:1 ratio. However, this does not determine the kind of molecule uniquely – dimethyl ether has the same ratios as ethanol, for instance.