neutrons and electrons given an element’s mass number or atomic number. If given this symbol - 4He – can you tell me how many neutrons and protons there are? If given this symbol 12Na – can you tell me how many neutrons and protons there are? Does this element exist? * What is an isotope? 2 atoms of the same element that differ in # neutrons * How are electrons arranged in an atom? Are they paired or unpaired? Which electrons make an element reactive? * How many electrons can reside in
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Chapter 1 * What is Chemistry? -it is the study of the composition of substances and the changes they undergo. * What are the 5 branches of chemistry? * Organic chemistry‚ inorganic chemistry‚ analytical chemistry‚ physical chemistry‚ biochemistry. * What is the difference between a theory and law? -a theory is a thoroughly tested explanation of why experiments give certain results. A scientific law is a concise statement that summarized the results of a broad spectrum of observations
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(a) Model of Atom The model of atom consists of 3 subatomic particle‚ namely the protons‚ electrons and neutrons. Of which‚ the protons and neutrons are found within the nucleus of the atom. As such‚ the nucleus of the atom has a positive charge‚ and most of the mass of the atom is located in the nucleus due to the insignificance of the weight of electrons. Surrounding the nucleus is a cloud of electrons‚ which move randomly around orbitals and sub orbitals at nearly the speed of light. Other than
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are created by the complete transfer of electrons from one atom to another. In this process of electron transfer‚ each atom becomes a ion that is isoelectronic with the nearest noble gas.‚ the substance is held together by electrostatic forces between the ions. The tendency for these ions to be formed by elements is corespondent to the octet rule‚ when atoms react‚‚ they tend to do so in such a way that they attain an outer shell containing eight electrons. The factors that effect the formation of
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incorporating in the pore. In addition‚ when we are speaking about electronic conductivity‚ it should be mentioned that electrons do not have an absolute monopoly on electrical conduction in solids. In literature still possible to meet a great uncertainty as to whether typical measurements allow researcher to conclude that conduction in a given m is due predominately to ions or to electrons. Many researchers have assumed that some of the MOFS can be treated as wide band gap semiconductors but other scientists
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definition of a covalent bond: A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding. For many molecules‚ the sharing of electrons allows each atom to attain the equivalent of a full outer shell‚ corresponding to a stable electronic configuration. (Source: http://en.wikipedia.org/wiki/Covalent_bond). With respect to that definition‚ one
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the problems with Dalton’s theory are that his second law that all atoms of the same element are the same is false because today we have found that there are other kinds of atoms called isotopes. An isotope is an atom that has the same amount of electrons and protons‚ but it has more neutrons that increase its atomic mass. Some examples of isotopes are Carbon 12‚ carbon 13‚ carbon 14‚ Uranium (234‚ 235‚ and 238) and lithium (6‚ 7). Carbon 14 is especially useful because we know its rate of decay and
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following atoms or ions would the 2s and 2p orbitals have the same energy? a) O2– b) H c) He d) Li+ e) F6+ 5. Which of the following electron excitations of the hydrogen atom requires light of the shortest wavelength? a) b) c) d) e) n = 2 to n = 3 n = 3 to n = 4 n = 4 to n = 20 n = 5 to n = 100 n = 4 to n = 1000 6. Which one of the following electron configurations is not valid? a) 1s2 2s2 2p2 b) 1s2 2s2 2p6 3s2 3p6 c) 1s2 2s2 2p6 3s2 3p2 d) 1s2 2s2 2p6 3s2 3p3 e) 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p8
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OF SOLIDS According to quantum free electron theory of metals‚ a electron in a metal experiences constant(or zero) potential and free to move inside the crystal but will not come out of the metal because an infinite potential exists at the surface. Bloch Theorem: According to this theorem‚ the periodic potentials due to the positive ions in metal have been considered. (i.e. the electrons moves in a periodic potential provided by lattice). If the electron moves through these ions‚ it experiences
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Carbon is denoted by the symbol C‚ is part of group 14 on the periodic table‚ and is the fourth most abundant element in the universe (by mass). Carbon has an electron configuration of 1s2‚ 2s2‚ 2p2. With 4 valance shell electrons it is expected to form 4 bonds‚ this means carbon is tetravalent. However the s orbitals do not form the same type of bond (with other atoms) as the p orbitals‚ this is because their shapes are different. For example CH4 would have the following bonds: C(s)-H(s)‚ C(s)-H(s)
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