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  2. Seesaw molecular geometry - Wikipedia

    en.wikipedia.org/wiki/Seesaw_molecular_geometry

    The seesaw geometry occurs when a molecule has a steric number of 5, with the central atom being bonded to 4 other atoms and 1 lone pair (AX 4 E 1 in AXE notation). An atom bonded to 5 other atoms (and no lone pairs) forms a trigonal bipyramid with two axial and three equatorial positions, but in the seesaw geometry one of the atoms is replaced ...

  3. Ligand - Wikipedia

    en.wikipedia.org/wiki/Ligand

    The number of times a polydentate ligand binds to a metal centre is symbolized by "κ n", where n indicates the number of sites by which a ligand attaches to a metal. EDTA 4− , when it is hexidentate, binds as a κ 6 -ligand, the amines and the carboxylate oxygen atoms are not contiguous.

  4. Langford pairing - Wikipedia

    en.wikipedia.org/wiki/Langford_pairing

    A Langford pairing for n = 4.. In combinatorial mathematics, a Langford pairing, also called a Langford sequence, is a permutation of the sequence of 2n numbers 1, 1, 2, 2, ..., n, n in which the two 1s are one unit apart, the two 2s are two units apart, and more generally the two copies of each number k are k units apart.

  5. VSEPR theory - Wikipedia

    en.wikipedia.org/wiki/VSEPR_theory

    [1]: 410–417 In VSEPR theory, a double bond or triple bond is treated as a single bonding group. [1] The sum of the number of atoms bonded to a central atom and the number of lone pairs formed by its nonbonding valence electrons is known as the central atom's steric number. The electron pairs (or groups if multiple bonds are present) are ...

  6. Bond order - Wikipedia

    en.wikipedia.org/wiki/Bond_order

    The bond order itself is the number of electron pairs (covalent bonds) between two atoms. [3] For example, in diatomic nitrogen N≡N, the bond order between the two nitrogen atoms is 3 (triple bond). In acetylene H–C≡C–H, the bond order between the two carbon atoms is also 3, and the C–H bond order is 1 (single bond).

  7. Sexy prime - Wikipedia

    en.wikipedia.org/wiki/Sexy_prime

    For example, the numbers 5 and 11 are a pair of sexy primes, because both are prime and =. The term "sexy prime" is a pun stemming from the Latin word for six: sex . If p + 2 or p + 4 (where p is the lower prime) is also prime, then the sexy prime is part of a prime triplet .

  8. Stable roommates problem - Wikipedia

    en.wikipedia.org/wiki/Stable_roommates_problem

    To find it, start at such a p 0 containing at least two individuals in their reduced list, and define recursively q i+1 to be the second on p i 's list and p i+1 to be the last on q i+1 's list, until this sequence repeats some p j, at which point a rotation is found: it is the sequence of pairs starting at the first occurrence of (p j, q j ...

  9. Lewis structure - Wikipedia

    en.wikipedia.org/wiki/Lewis_structure

    Each bond consists of a pair of electrons, so if t is the total number of electrons to be placed and n is the number of single bonds just drawn, t−2n electrons remain to be placed. These are temporarily drawn as dots, one per electron, to a maximum of eight per atom (two in the case of hydrogen), minus two for each bond.