Download a copy of the Kenya High, Alliance, and Lenana Pre-Mock (KALA); Biology PP1,PP2 & PP3 Question Papers with well coordinated Marking Schemes attached. This is good revision material for your upcoming exams.

ADDITION REACTIONS TO POLARIZED MULTIPLE BONDS The electron flow paths for addition The AdE2 Reaction: Electron Flow Pathways AE + A N

Download a copy of the Kenya High, Alliance, and Lenana MOCK (KALA); Biology PP1,PP2 & PP3 Question Papers with well coordinated Marking Schemes attached. This is good revision material for your upcoming exams.

BASIC RULES FOR MECHANISM STUDIES IN ORGANIC CHEMISTRY Carbon has 4 bonds – it is neutral. If it has 3 bonds, then look at number of electrons. None – positive - carbocation 1 electron – no charge – free radical 2 electrons – negative - carbanion Curly arrow : Atom where the arrow comes from – becomes less negative or positive. If it was an anion – atom becomes neutral

Many authorities predict that applications of nanotechnologies will ultimately pervade virtually every aspect of life and will enable dramatic advances to be realized in most areas of communication, health, manufacturing, materials and knowledge-based technologies. Even if this is only partially true, there is an obvious need to provide industry and research with suitable tools to assist the development, application and communication of the technologies. One essential tool in this armoury will be the harmonization of the terminology and definitions used in order to promote their common understanding and consistent usage. This terminology includes terms that are either specific to the sector covered by the title or are used with a specific meaning in the field of nanotechnology. It is one of a series of terminology PASs covering many different aspects of nanotechnologies. This terminology attempts not to include terms that are used in a manner consistent with a definition given in the Oxford English Dictionary [1], and terms that already have well established meanings and to which the addition of the prefix “nano” changes only the scale to which they apply but does not otherwise change their meaningThe multidisciplinary nature of nanotechnologies can lead to confusion as to the precise meaning of some terms because of differences in usage between disciplines. Users are advised that, in order to support the standardization of terminology, this PAS provides single definitions wherever possible

Nanoparticles are defined by the worldwide federation of national standards bodies, the International Organization for Standardization (ISO), as nanoobjects with all external dimensions in the nanoscale, where the lengths of the longest andshortest axes of nanoobjects do not differ significantly . Though nanoscale is basically ranged from 1 to 100 nm, nanoparticles can be categorized by three size ranges: larger than 500 nm, between 100 and 500 nm, and between 1 and 100 nm (European Commission, 2010). With respect to the size and the size distribution, nanoparticles may exhibit size-related intensive properties. If they are small enough to confine their electrons, they produce quantum effects and exhibit unexpected properties, for example, gold nanoparticles appear red in solution (see, for instance, Eustis and El-Sayed, 2006), and melt at much lower temperatures than that in slab form (Buffat and Borel, 1976). The high surface-area-to-volume ratio of nanoparticles provides the significant changes in properties related to contact/surface area, such as catalytic (Astruc, 2008),surface-enhanced plasmon resonance (Melaine et al., 2015), etc.

An elimination is the loss of two atoms or groups from a molecule, which will typically result in the formation of a new bond.

Lewis Structures A Lewis structure shows what atoms are connected to each other, and it shows where the electrons in the molecule reside. Single bonds between two atoms are represented with a single line, signifying two shared electrons; double bonds are represented with a double line, signifying four shared electrons; and triple bonds are represented with a triple line, signifying six shared. Nonbonding electrons are indicated with dots on the atoms on which they reside.

Nanoscience is the emerging science of objects that are intermediate in size between the largest molecules and the smallest structures that can be fabricated by current photolithography; that is, the science of objects with smallest dimensions ranging from a few nanometers to less than 100 nanometers.[1–3] In chemistry, this range of sizes has historically been associated with colloids, micelles, polymer molecules, phase-separated regions in block copolymers, and similar structures—typically, very large molecules, or aggregates of many molecules. More recently, structures such as buckytubes, silicon nanorods, and compound semi conductor quantum dots have emerged as particularly interesting classes of nanostructures. In physics and electrical engineering, nanoscience is most often associated with quantum behavior, and the behavior of electrons and photons in nanoscale structures. Biology and biochemistry also have a deep interest in nanostructures as components of the cell; many of the most interesting structures in biology—from DNA and viruses to subcellular organelles and gap junctions—can be considered as nanostructures.

In this type of reaction, a nucleophile reacts with haloalkane (the substrate) having a partial positive charge on the carbon atom bonded to halogen. A substitution reaction takes place and halogen atom, called leaving group departs as halide ion. Since the substitution reaction is initiated by a nucleophile, it is called nucleophilic substitution reaction