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  2. Target hardening - Wikipedia

    en.wikipedia.org/wiki/Target_hardening

    Target hardening, also referred to simply as hardening when made clear by the context, is a term used by police officers, those working in security, and the military referring to the strengthening of the security of a building or installation in order to protect it in the event of attack or reduce the risk of theft.

  3. Chemical polarity - Wikipedia

    en.wikipedia.org/wiki/Chemical_polarity

    Nonpolar bonds generally occur when the difference in electronegativity between the two atoms is less than 0.5; Polar bonds generally occur when the difference in electronegativity between the two atoms is roughly between 0.5 and 2.0; Ionic bonds generally occur when the difference in electronegativity between the two atoms is greater than 2.0

  4. Rockwell scale - Wikipedia

    en.wikipedia.org/wiki/Rockwell_scale

    A Rockwell hardness tester. The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test measures the depth of penetration of an indenter under a large load (major load) compared to the penetration made by a preload (minor load). [1]

  5. Molecular geometry - Wikipedia

    en.wikipedia.org/wiki/Molecular_geometry

    Molecular geometries can be specified in terms of 'bond lengths', 'bond angles' and 'torsional angles'. The bond length is defined to be the average distance between the nuclei of two atoms bonded together in any given molecule. A bond angle is the angle formed between three atoms across at least two bonds.

  6. Bonding in solids - Wikipedia

    en.wikipedia.org/wiki/Bonding_in_solids

    Intermediate organization of covalent bonds: Regarding the organization of covalent bonds, recall that classic molecular solids, as stated above, consist of small, non-polar covalent molecules. The example given, paraffin wax , is a member of a family of hydrocarbon molecules of differing chain lengths, with high-density polyethylene at the ...

  7. Infrared spectroscopy correlation table - Wikipedia

    en.wikipedia.org/wiki/Infrared_spectroscopy...

    An infrared spectroscopy correlation table (or table of infrared absorption frequencies) is a list of absorption peaks and frequencies, typically reported in wavenumber, for common types of molecular bonds and functional groups.

  8. Hydrophobicity scales - Wikipedia

    en.wikipedia.org/wiki/Hydrophobicity_scales

    The effect originates from the disruption of highly dynamic hydrogen bonds between molecules of liquid water. Polar chemical groups, such as OH group in methanol do not cause the hydrophobic effect. However, a pure hydrocarbon molecule, for example hexane, cannot accept or donate hydrogen bonds to water. Introduction of hexane into water causes ...

  9. VSEPR theory - Wikipedia

    en.wikipedia.org/wiki/VSEPR_theory

    Shows location of unpaired electrons, bonded atoms, and bond angles. The bond angle for water is 104.5°. Valence shell electron pair repulsion ( VSEPR ) theory ( / ˈ v ɛ s p ər , v ə ˈ s ɛ p ər / VESP -ər , [ 1 ] : 410 və- SEP -ər [ 2 ] ) is a model used in chemistry to predict the geometry of individual molecules from the number of ...