electrical/heat conductors • high melting/boiling temperatures • transparent to visible light • strong IR absorption • soluble in polar solvents (e.g.‚ water) Bonding in solids: Covalent solids Atoms in the crystal are held together by covalent bonding C atoms in diamond form a tetragonal crystal structure Properties of covalent crystals: • very hard and stable • high melting point • good insulators • do not absorb light • larger cohesive energies (~10 eV) than in ionic crystals Bonding in solids:
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Organisms A hydrogen bond is an intermolecular bond and is formed when a charged part of a molecule having polar covalent bonds‚ forms an electrostatic attraction with a molecule of opposite charge‚ generally with fluorine‚ oxygen and nitrogen. Molecules having non polar covalent bonds do not form hydrogen bonds. Hydrogen bonds are classified as weak bonds as they are easily and rapidly formed and broken‚ however the cumulative effects of large numbers of these bonds can be enormous. Properties
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is an excellent electrical conductor because every atom in a diamond is bonded to its neighbours by four strong covalent bonds leaving no free electrons and no ions. That’s why diamond does not conduct electricity Graphite is soft because they are built in layers. Graphite is a good electrical conductor because each carbon atom is bonded into its layer with three strong covalent bonds. This leaves each atom with a spare electron‚ which together form a delocalised ‘sea’ of electrons loosely bonding
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Introduction Notes What is Science? Study of/tool to understand/body of knowledge/process to understand the natural world What do Scientists do? Make observations Attempt to discern patters Assume the future is like the past What is Biology? The study of life What is Life? Not ever clearly defined Characteristics of living systems: Highly organized Huge energy users 90% of food we eat is used to keep us going Development Development from a single cell to billons of cells Reproduction
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Abacus Inc. has asked you price a 5 year bullet bond issue for them‚ with Price‚ Yield to Maturity and Modified Duration. There are no comparable existing issues in the secondary market either by Abacus or a competitor and so you will need to price the issue from scratch. You have the following set of US Treasury bond data and consultations with your Bank Equity Analyst and Debt Analyst suggest that a Z-spread for Abacus of 200 bps over Treasuries and a coupon rate of 6.5% should be appropriate
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hydrogen bonding occurs between the hydrogen and an oxygen atom in the same molecule. an oxygen atom in a different molecule. a hydrogen atom in a different molecule. a hydrogen atom in the same molecule. 5 out of 5 Correct!! Question 9 of 20 Covalent bonds form when one atom _________ its
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example‚ polystyrene. There are four classifications of hydrocarbons; saturated hydrocarbons or alkanes‚ unsaturated hydrocarbons or alkenes and alkynes‚ cycloalkanes‚ and aromatic hydrocarbons or arenes. The different between these groups is in the bond types between the carbons. Objective: 1- To observe the flame of cyclohexane and cyclohexene. 2- To observe the effect of adding sulphuric acid on cyclohexane and cyclohexene. Apparatus Needed: Test tubes and rack‚ watch glass‚ and matches. Chemical
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(A) 1.30 (B) 2.60 (C) 3.9 (D) 1.20 (7) Bond Order for CO+ and NO+ are respectively (A) 3.5‚ 3.0 (B) 2.5‚ 3.0 (C) 2.5‚ 2.5 (D) 3.0‚ 2.5 (8) Bond Order for N2+ and N2- are same. Which relation is correct for N2+ and N2- ? (A) Bond Energy of N2+ = Bond Energy of N2- (B) Bond Energy of N2+ > Bond Energy of N2- (C) Bond Energy of N2+ < Bond Energy of N2- (D) Bond Energy of N2+ < > Bond Energy of N2- (9) The electron gain enthalpy of fluorine
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Shrinkage is the contraction in the dimension of the fabric due to usage. These are the reasons for shrinkage: • In case of a fabric‚ the warp yarns are under much strain due to interlacement than the weft yarns. Hence when a fabric is allowed to shrink‚ the warp yarn shrinkage will be more than weft yarns. • To overcome this fabric is extended in widthwise to some extent in the stenter machine during the finishing process. Then it is subjected to the preshrink process. Various mechanical
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either ionic or covalent bonds to attain a complete outer shell (octet rule for second row elements). • Ionic bonds result from the transfer of electrons from one element to another. • Covalent bonds result from the sharing of electrons between two nuclei. 2 Valence Electrons • Second row elements can have no more than eight electrons around them. For neutral molecules‚ this has two consequences: • Atoms with one‚ two‚ three‚ or four valence electrons form one‚ two‚ three‚ or four bonds‚ respectively
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