Theory Building models of molecules are useful for visualizing how atoms are connected in three-dimensional space called molecular geometry‚ which is best predicted by Valence-Shell Electron-Pair Repulsion (VSPER) theory. The following are the sets of rules summarizing thsi theory: ● Consider molecules and ions where two or more atoms are bonded to a central atom. ● The electron pairs in the valence shell of the central atom are assumed to position as far apart as possible because electron pair
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GREEK PHILOSOPHY What Is Philosophy? Philosophy: The studies of Greco-Roman thinkers on activities and inquiries. It is also the rational investigation of the truths and principles of being‚ knowledge‚ or conduct. Philosophy focuses on three main types: Stoicism Skepticism Epicurean Philosophy consists of these philosophical areas: Metaphysics Materialism Idealism Epistemology Empiricism Rationalism Ethics Hedonism Cynicism Three Main Types Stoicism Refers to the knowledge
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of all the atoms present in one molecule of that compound. Example: the molecular mass of sodium bromide‚ NaBr‚ is 103‚ which represents the sum of the atomic mass of sodium (23) plus that of bromide (80). * Calculating the Molecular Mass (Formula Mass) of a Compound * To find the molecular mass of a compound‚ add the atomic masses of all the atoms that are present in that compound. * In the compound H2O‚ the molecular mass can be calculated by adding the mass of two atoms of hydrogen
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arrangement of terminal atoms‚ or groups of atoms about a central atom in a covalent compound‚ or charged ion‚ is determined solely by the repulsions between electron pairs present in the valence shell of the central atom. The number of electron pairs around the central atom can be determined by writing the Lewis structure for the molecule. The geometry of the molecule depends on the number of bonding groups (pairs of electrons) and the number of nonbonding electrons on the central atom. The five important
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formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms. The bound state implies a net attractive force between the atoms ... a chemical bond. The two extreme cases of chemical bonds are: Covalent bond: bond in which one or more pairs of electrons are shared by two atoms. Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom‚ resulting in positive and negative
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substitution of one or more atoms of hydrogen with hydrocarbon radicals. Therefore‚ if one hydrogen atom from methane is replaced by a methyl radical‚ -CH3‚ the hydrocarbon (superior to methane) will have the composition C2H6‚ named ethane. The alkanes can be: with a continuous chain‚ if all the carbon atoms are bound with at most two other carbon atoms‚ and with a branched chain‚ if one or more carbon atoms from the molecule are bound with at least two other carbon atoms. Such an isomerism of chain
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flows in an aqueous solution of ionic compounds‚ the metal ions appears at the negative electrode (cathode). - The metal exists in the solution as positively charged particles known as ions. - A 1+ ion plus one unit of electricity gives one metal atom. - Low pressures gases conduct electricity very well. - The glass of containing vessel opposite the cathode (negatives electrode) glowed when the applied potential difference (voltage) was sufficiently high. - Solid objects cast shadows between
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The Bohr Model An atom* is the smallest particle of an element that retains the characteristics of that element. Each of the known 118 elements has atoms that are different from the atoms of all other elements. This gives each element a unique atomic structure. According to the classical Bohr model‚ atoms have a planetary type of structure that consists of a central nucleus surrounded by orbiting electrons‚ as illustrated in Figure 1–1. The nucleusconsists of positively charged particles called
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is electricity? Where does it come from? How does it work? Before we understand all that‚ we need to know a little bit about atoms and their structure. All matter is made up of atoms‚ and atoms are made up of smaller particles. The three main particles making up an atom are the proton‚ the neutron and the electron. Electrons spin around the center‚ or nucleus‚ of atoms‚ in the same way the moon spins around the earth. The nucleus is made up of neutrons and protons. Electrons contain a negative
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model of the atom‚ electrons in an atom (1) travel in defined circles (3) have a positive charge (2) are most likely found in an excited state (4) are located in orbitals outside the nucleus 2. ____ What is the total charge of the nucleus of a carbon atom? (1) –6 (2) 0 (3) +6 (4) +12 3. ____ When an atom loses one or more electrons‚ this atom becomes a (1) positive ion with a radius smaller than the radius of this atom (2) positive ion with a radius larger than the radius of this atom (3) negative
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