Atoms chemical formulas

The expression that shows the number and kind of each atom in a molecule is the chemical formula. Chemical formulas use the chemical symbol of the atom to express the type of atom and a subscript following the symbol to express the number of atoms in the molecule. If there is only one of a type of atom, no subscript is used. In addition to the number and type of atom, chemical formulas can (but don t have to) suggest the arrangement of the atoms. 

Lewis structure (Section 1 3) A chemical formula in which electrons are represented by dots Two dots (or a line) be tween two atoms represent a covalent bond in a Lewis structure Unshared electrons are explicitly shown and sta ble Lewis structures are those in which the octet rule is sat isfied... 

Molecular formula (Section 1 7) Chemical formula in which subscnpts are used to indicate the number of atoms of each element present in one molecule In organic compounds carbon is cited first hydrogen second and the remaining el ements in alphabetical order... 

The system of indexing molecules is, first, according to the number of atoms in the molecule. Then, with the chemical formula written in what seems a natural way, they are ordered alphabetically in order of the atoms as they appear in the formula. 

For most molecules with more than three atoms the name of the molecule is given in parentheses after the chemical formula. In most cases, only the common and not the systematic name is given so that, for example, C2H4 is called ethylene and not ethene. 

Properties. Boron carbide has a rhombohedral stmcture consisting of an array of nearly regular icosahedra, each having twelve boron atoms at the vertices and three carbon atoms ia a linear chain outside the icosahedra (3,4,6,7). Thus a descriptive chemical formula would be [12075-36-4]. 

An important approach to the graphic representation of molecules is the use of a connection table. A connection table is a data base that stores the available bond types and hybridizations for individual atoms. Using the chemical formula and the connection table, molecular stmctures may be generated through interactive graphics in a menu-driven environment (31—33) or by using a linear input of code words (34,35). The connection table approach may be carried to the next step, computer-aided molecular design (CAMD) (36). 

The phase diagram for the copper-antimony system is shown on the next page. The phase diagram contains the intermetallic compound marked "X" on the diagram. Determine the chemical formula of this compound. The atomic weights of copper and antimony are 63.54 and 121.75 respectively. 

Panel 1.1 The 20 different amino acids that occur in proteins. Only side chains are shown, except for the first amino acid, alanine, where all atoms are shown. The bond from the side chain to Ca is red. A ball-and stick model, the chemical formula, the full name, and the three-letter and one-letter codes are given for each amino acid. 

Figure S.22 Chemical formula for sialic acid (a-5-n-acetylneuramlnlc acid) drawn In approximately the same orientation as the ball and stick models in Figure 5.24. Ri and Rz which are H atoms in sialic acid, denote substituents introduced to design tightly bound inhibitors. These are large and hydrophobic as shown in Figure 5.24.

The formula weight of an element (or a compound or a species) is obtained as the sum of the weight contributions from the constituent atoms making up its chemical formula. The formula weight of an element is its atomic weight and that of a compound is its molecular weight. 

Spatial congruence of C-H graphs is applied essentially only in chemical formulas which represent a compound of carbon atoms and atoms of valence 1 (or radicals of valence 1). In this case condition (IV), besides (I), (II), (III), adds another restriction not only the relationships are important but also the spatial arrangement of the bonds. The spatial interpretation of the congruence of C-H graphs coincides with the interpretation of the chemical formula as stereoformula. I use stereoisomers in this sense. For example, the number of different stereoisomers is equal to the number of spati-... 

Alkanes are a class of saturated hydrocarbons with the general formula C H2n. -2- They contain no functional groups, are relatively inert, and can be either straight-chain (normal) or branched. Alkanes are named by a series of IUPAC rules of nomenclature. Compounds that have the same chemical formula but different structures are called isomers. More specifically, compounds such as butane and isobutane, which differ in their connections between atoms, are called constitutional isomers. 

To this point, our study of chemistry has been largely qualitative, involving very few calculations. However, chemistry is a quantitative science. Atoms of elements differ from one another not only in composition (number of protons, electrons, neutrons), but also in mass. Chemical formulas of compounds tell us not only the atom ratios in which elements are present but also the mass ratios. 

The general topic of this chapter is stoichiometry (stoy-key-OM-e-tree), the study of mass relations in chemistry. Whether dealing with atomic masses (Section 3.1), molar masses (Section 3.2), chemical formulas (Section 3.3), or chemical reactions (Section 3.4), you will be answering some very practical questions that ask how much or how many—." For example—... 

The physical and chemical properties of complex ions and of the coordination compounds they form depend on the spatial orientation of ligands around the central metal atom. Here we consider the geometries associated with the coordination numbers 2,4, and 6. With that background, we then examine the phenomenon of geometric isomerism, in which two or more complex ions have the same chemical formula but different properties because of their different geometries. 

Stearic acid is a member of the group called fatty acids. These are hydrocarbon chains (chains made of repeated units of a carbon atom and two hydrogen atoms) with a carboxyl group at one end. A carboxyl group is the COOH in the chemical formula. It is what turns the hydrocarbon chain into an organic acid. 

The chemical formula depicted above is that of trilinolein, a representative component of vegetable oils. Bromine atoms attach at various places on the molecule to form BVO. The amount of bromine is controlled to produce the desired density. 

The chemical formula of a compound represents its composition in terms of chemical symbols. Subscripts show the numbers of atoms of each element present in the smallest unit that is representative of the compound. For molecular compounds, it is common to give the molecular formula, a chemical formula that shows how many atoms of each type of element are present in a single molecule of the compound. For instance, the molecular formula for water is H20 each molecule contains one O atom and two H atoms. The molecular formula for estrone, a female sex hormone, is Clgl-I2202, showing that a single molecule of estrone consists of 18 C atoms, 22 FI atoms, and 2 O atoms. A molecule of a male sex hormone, testosterone, differs by only a few atoms its molecular formula is (lyH2802. Think of the consequences of that tiny difference ... 

The chemical formula of an ionic compound shows the ratio of the numbers of atoms of each element present in one formula unit. A formula unit of an ionic compound is a group of ions with the same number of atoms of each element as appears in its formula. 

C.3 The compound xanthophyll is a yellow compound found in bird feathers and flowers. Xanthophyll contains atoms of carbon, hydrogen, and oxygen in the ratio 20 28 1. Its molecules each have six oxygen atoms. Write the chemical formula of xanthophyll. 

J 5 Interpret chemical formulas in reference to the number of each type of atom present. 

Now there are four H atoms, two Na atoms, and two O atoms on each side, and the equation conforms to the law of conservation of mass. The number multiplying an entire chemical formula in a chemical equation (for example, the 2 multiplying H20) is called the stoichiometric coefficient of the substance. A coefficient of 1 (as for H2) is not written explicitly. 

A chemical equation expresses a chemical reaction in terms of chemical formulas the stoichiometric coefficients are chosen to show that atoms are neither created nor destroyed in the reaction. 

Although they are built from the same numbers and kinds of atoms, structural isomers have different chemical formulas, because the formulas show how the atoms are grouped in or outside the coordination sphere. Stereoisomers, on the other hand, have the same formulas, because their atoms have the same partners in the coordination spheres only the spatial arrangement of the ligands differs. There are two types of stereoisomerism, geometrical and optical. 

In a balanced chemical equation (commonly called a chemical equation ), the same number of atoms of each element appears on both sides of the equation, chemical equilibrium A dynamic equilibrium between reactants and products in a chemical reaction, chemical formula A collection of chemical symbols and subscripts that shows the composition of a substance. See also condensed structural formula empirical formula,- molecular formula structural formula. 

Stem-Gerlach experiment The demonstration of the quantization of electron spin by passing a beam of atoms through a magnetic field, stick structure See line structure. stock solution A solution stored in concentrated form, stoichiometric coefficients The numbers multiplying chemical formulas in a chemical equation. 

Bearing in mind that the relative sizes of the ions permit isomorphous replacement of OH by F but not by Cl, we write with considerable confidence the formula (Si, Al, Fe, P)18O20(OH, F)laCl, which agrees well with analyses 1, 2, and 3. Inasmuch as aluminium (as well as phosphorus) may replace silicon with coordination number 4, it is evident that there are at least five silicon atoms in the unit, corresponding to the chemical formula... 

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