Release only ONE color of light Produce very little heat What is an LED? They are semiconductor devices that can convert electrical energy directly into light due to the nature of the bonding that occurs in the semiconductor solid. Type of bonding is directly related to conductivity of solid. Bonding in Elemental Solids Electronegativity – the ability of an atom to attract electrons to itself. Atoms with low e.n. (metals) don’t hold valence electrons tightly valence electron
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elements are brought together under conditions that will favour a reaction and they have similar electronegativities‚ which type of chemical bond is most likely to form? a) nonpolar covalent bond b) polar covalent bond c) ionic bond d) London forces e) hydrogen bond 5. How many electrons are involved in each covalent bond? a) 1 b) 2 c) 4 d) 6 e) 8 6. An amino acid always has an amino group‚ as its name suggests. What other group is also present in all amino acids? a) a methyl group
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receptors. Theme 4: Homeostasis maintains internal stability: maintaining a relatively internal environment even though the external environment is variable. Chapter 2 1. Explain chemical bonding in terms of covalent‚ ionic‚ and hydrogen bonds as well as discuss Van der Waals forces. Chemical bonding involves the
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I. DISCUSSION: Differences between organic and inorganic compounds based on structure‚ type of bond and some common physical and chemical properties. II. PROCEDURE: A. SOLUBILITY 1. To 2 mL. each of the following solvents: water‚ ethyl alcohol and ether‚ add a pinch of benzoic acid and shake.
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neutrons‚ both of which are assigned one atomic mass unit 15. The factor that determines whether an atom will be chemically reactive is the valence shell (an atoms outer shell) 16. The bond that results from sharing of electrons is a covalent bond 17. An ionic bond is a chemical bond in which ions are attracted to one another by opposite charges (negative and positive) 18. The interaction that causes water
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Chapter 2 22. A student heats 0.5585 g of iron with 0.3550 g of sulfur. She reports that she obtains 0.8792 g of iron sulfide and recovers 0.0433 g of unreacted sulfur. Show by calculation whether or not her results obey the law of conservation of mass. Total mass initial = 0.5585 g + 0.3550 g = 0.9135 g Total mass final = 0.8792 g + 0.0433 g = 0.9225 g These two values should be equal by the law of conservation of mass. These results do not obey the law of conservation of mass. Possibly she
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Cup o’ Noodles: Through the Eyes of a Chemist Background: Before completing this experiment‚ one must know about chemical formulas‚ ionic bonding‚ solutions and moles to understand the results of this experiment. A chemical formula is the symbol for compounds and elements. It tells chemists how many atoms are in a chemical compound‚ formula unit or molecular compound. In a chemical formula a subscript indicates how many atoms there are of an element before it. The coefficient in a chemical formula
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electricity | Non-conductor | Conductivity of solution | Conducts electricity in solution | Non-Conductor | Non-conductor | Non-conductor | Conducts electricity in solution | Non-Conductor | Classification | Ionic bond | Non-polar molecular solid | Covalent bond | Polar molecular solid | Ionic bond | Metallic bond | Calculations No calculations were required in this experiment. Discussion The flame test was undertaken
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electrons and‚ therefore‚ stronger van der Waal’s forces which require more energy to overcome them • Electronegativity is the ability of an atom to attract the electrons in a covalent bond • Down Group 7‚ the shared electrons are further from the nucleus and more shielded. There is a weaker attraction for the bonding electrons down the Group 2) Trends in chemical properties of the elements • The Group 7 elements are oxidising agents which gain an electron when they react •
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Valence electrons octet rule exceptions P and S can have 10 or 12 valence e- B and Al (Group 3) can have 6 valence e- electronegativity- how much an atom wants e- < 0.5 = nonpolar‚ covalent (i.e. H2) 0.5 - 1.9 = polar covalent direction of polarity (using arrow and delta symbol) overall dipole > 1.9 = ionic formation of ions fish-hook arrow Lewis structure formal charge Functional Groups Molecular Shape VSEPR (Valence Shell e- Pair Repulsion) bonds contain e- (negative) these repel
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