Atom

). “The amount of a pure substance is expressed by the SI base unit of the mole”. One mole of a substance contains 6.02 x10^23 particles of the substance. That number is known as Avogadro’s number ("Amount of." SI Units Explained). “The number of atoms or other particles in a mole is the same for all substances” (The Editors of Encyclopædia Britannica). That…

With a rise in temperature, the atoms with in crystal vibrate more vigorously, resulting in an expansion of thermal ellipsoids. As such, the atomic volume increases and the internal crystal structure changes through tetrahedral tilting. An ordered structure with high level of symmetry…

Due to his discovery this led to many other scientists to look into subatomic particles and examine them closely. Later J.J. had proposed his own model of the atom but was later proved wrong by Ernst Rutherford. J.J. depicted the atom as electrons orbiting a positively charged nucleus and compared it to plum pudding wit the electrons being the plums and the pudding being the positively charged nucleus. He also created a new device that could analyze…

 Comment: The three bonds (one solid line, one wedged line and one dashed line) that are attached to the + carbon atom are turned inside out. If the starting material has Br on the right side of the + carbon atom, the final product will have OH on the left side of the + carbon atom and vice versa.  Comment: There is only one hump for the energy profile of an SN2 reaction. As we shall see later, there are two humps for the energy profile of an SN1 reaction. One easy way to…

Science Matters: Achieving Scientific Literacy Robert M. Hazen and James Trefil wanted to write a book a book that explained the fundamentals of science without being too obscure or specialized. Science Matters : Achieving Scientific Literacy is a book for the general reader that is informative enough to be a popular textbook for introductory courses in high school and college, and yet well-written enough to appeal to general readers uncomfortable with complicated mathematics. Anyone can…

loops and a few protruding amino acid side chains. Q6) The interface between subunits probably contains the binding site for activators and inhibitors. Q7) Since most of the effector molecules have negatively charged atoms (such as ADP with the negatively charged oxygen atoms on the phosphate groups), it is likely that positively charged residues will need to bind to them. Since many basic amino acids have side chains that are positive under cellular conditions, it is likely that basic…

The Physics of PET Scans All elements are composed of atoms, which are composed of small particles called protons, neutrons, and electrons. The nucleus of an atom is made of a tightly packed collection of protons and neutrons. You would think that with positively charged protons being packed so closely together the nucleus would fall apart, however this is not the case. There is an attractive force called the “nuclear force” which is able to overcome the repulsive force of the adjacent…

these are man-made but most have been discovered. The things that make each element have a distinguished quality, is that they have different types of atoms. Atoms are the basic building blocks of matter, and cannot be broken down to a further point. Each atom is made up of protons, neutrons, and electrons. Protons and neutrons are in the center of the atom, while the electrons stay far apart from each other, and revolve around the center. This is called the Bohr model, made by Neil Bohr in…

The measure of the melting/ boiling point is also a measure of how strong the attraction forces are between atoms or molecules. From the strongest to the weakest, the four types of intermolecular forces used in a molecule that can affect the boiling/melting points of a solid or liquid are London dispersion, dipole-dipole, hydrogen bonds, and ionic bonds. The…

Introduction Water is a chemical compound comprised of two hydrogen atoms and one oxygen atom and is written in the chemical equation form of H2O. Water has a tetrahedral molecular shape which is also known as tetrahedral electron pair geometry (Ophardt, 2003). This arrangement is due to valence electron pairs, mutually repelling each other at a 109.5-degree angle. This repulsion is caused by a non-bonding pair of electrons and two hydrogen atoms which in turn repel against each other to form…