ATOM EXAMPLES FREE
However, this assumes the atom exhibits a spherical shape, which is only obeyed for atoms in a vacuum or free space. The atomic radius of a chemical element measures the distance out to which the electron cloud extends from the nucleus. It must be noted that atoms lack a well-defined outer boundary. For uranium atom, the Van der Waals radius is about 186 pm = 1.86 ×10 −10 m. The volume of an atom is about 15 orders of magnitude larger than the volume of a nucleus. The ångström is not a part of the SI system of units, but it can generally be considered part of the metric system. The atoms are about 10 – 10 meters (or 10 – 8 centimeters) in size, corresponding to the angstrom. The number of atoms in 1 mole (e.g., 12 grams of carbon) of a substance is equal to the Avogadro’s constant, equal to 6.022 x 10 23.Unstable nuclei must undergo nuclear decay (radioactive decay) to stabilize themselves, and it is a random and natural process.There are only certain combinations of neutrons and protons which form stable nuclei.To determine the stability of an isotope, you can use the ratio neutron/proton (N/Z). It is needed to find the ratio of neutrons to protons to identify the stability of an isotope. Nuclear stability is a concept that helps to identify the stability of an isotope.The nuclear properties (atomic mass, nuclear cross-sections) of the element are determined by the number of protons ( atomic number) and the number of neutrons ( neutron number).The number of electrons and their arrangement in the electron cloud is responsible for the chemical behavior of atoms.The atoms consist of two parts, an atomic nucleus, and an electron cloud.The physical world is composed of combinations of various subatomic or fundamental particles, and these are the smallest building blocks of matter.The atoms consist of two parts, an atomic nucleus, and an electron cloud. N polypeptides (internal, or terminal).The atoms are defined as the smallest constituents of ordinary matter, which can be divided without releasing electrically charged particles. Hits single a.a.s and specific residues w/i Or Glycine, they have their own SMARTS (see side chain list). side chain from the 18_standard_side_chains list to hit a specific standard a.a. Hits single a.a.s and specific residues w/in polypeptides (internal, or terminal).ĭipeptide group. Here we use the disconnection symbol (".") to match two separate unbonded identical patterns.įor use w/ non-standard a.a. ) !$(NC#)] Not amide (C not double bonded to a hetero-atom), not ammonium ion (N must be 3-connected), not ammonia (N's H-count can't be 3), not cyanamide (C not triple bonded to a hetero-atom) Also note that "&" (and) is the dafault opperator and is higher precedence that "," (or), which is higher precedence than " " (and). Primary or secondary is specified by N's H-count (H2 & H1 respectively). Not ammonium ion (N must be 3-connected), not ammonia (H count can't be 3). Hits atoms that don't have exactly one attached hydrogen. Hits atoms that have a positive charge and exactly one attached hydrogen: F(F) Won't hit carbonic acid or combination carbonic acid/ester Hits conjugate bases of carboxylic, carbamic, and carbonic acids.Ĭarbonic Acid, Carbonic Ester, or combination Hits carbamic esters, acids, and zwitterions Or ester, anhydride Won't hit aldehyde or ketone. Hits ester, carboxylic acid, carbonic acid or ester, carbamic acid Hits amide, carbamic acid/ester, poly peptide (except formic), acyl halides (acid halides). Hits aldehyde, ketone, carboxylic acid (except formic), anhydride Hits carboxylic acid, ester, ketone, aldehyde, carbonicĪcid/ester,anhydride, carbamic acid/ester, acyl halide, amide. Please send corrections, improvements, additions, and questions Functional Groups by ElementĪrene (Ar, aryl-, aromatic hydrocarbons) These SMARTS have been tested, but they may still contain errors. Many potentially useful example SMARTS which may be used to When using SMARTS to do searches, it is often helpful to haveĮxample queries from which to start.