as mercury and cesium. Density of metals is not similar also. For example‚ sodium has density of 0.97g/cm3 while lead has density of 11.4g/cm3. Melting point of sodium is 98.0oC while for lead it is 327.6oC. Metals have the capability to lose electrons when they react with non-metals such as O2‚ halogens‚ water‚ acids and other metal cations. Metals react with non-metals but each to a different extent. The most reactive metals are alkali metals (group1A‚ where group is a vertical
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10 Chapter 9: Chemical Bonding I – Lewis Theory 1. Which of the following statements is TRUE? a) A covalent bond is formed through the transfer of electrons from one atom to another. b) A pair of electrons involved in a covalent bond are sometimes referred to as "lone pairs." c) It is not possible for two atoms to share more than two electrons. e) A covalent bond has a lower potential energy than the two separate atoms. d) Single bonds are shorter than double bonds. 2. Which of the following
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particles must give way to the idea that electrons and atoms have wave-like properties‚ and that the wavelength associated with the particle depends on the particle’s momentum. Describing the interactions of the waves corresponding to individual electrons is at the heart of molecular wave mechanics. When the electron waves in a region of the molecule overlap in a constructive way‚ like water waves reinforcing each other‚ there is greater likelihood of finding the electrons in that region. The challenge
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1 Class XII: Chemistry Chapter 1: The Solid State Concept 1. Solid: Solid is a state of matter in which the constituting particles are arranged very closely. The constituent particles can be atoms‚ molecules or ions. Properties of solids: a. They have definite mass‚ volume and shape. b. Intermolecular distances are short and hence the intermolecular forces are strong. c. Their constituent particles have fixed positions and can only oscillate about their mean positions. d. They are incompressible
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neutrons and electrons. * Define proton number and nucleon number. * Use proton number and the simple structure of atoms to explain the basis of the Periodic Table (Ref. Z=1 to 20) * Define isotopes. * State the two types of isotopes as being radioactive and non-radioactive. * State one medical and one industrial use of radioactive isotopes. * Describe radioactive isotopes as a source of energy. eg. 235U * Describe the build-up of electrons in `shells` and
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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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Classification of matter • All the objects and substances that we see in the world are made of matter. • This matter can be classified according to whether it is a mixture or a pure substance. • A mixture is a combination of two or more substances‚ where these substances are not bonded (or joined) to each other and no chemical reaction occurs between the substances. Examples of mixtures are air (a mixture of different gases) and cereal in milk. • The main characteristics
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intermolecular forces. 1+1 1 1 (ii) There are mobile electrons in solid sodium but the ions in solid sodium chloride are not free to move/ solid sodium chloride has no mobile ion. 1 1 (iii) Tetrachloromethane which is a covalent compound‚ does not possess any mobile electrons (ions)/ exists as (discrete) molecules in liquid state‚ therefore is not an electrical conductor 1 1993 - 4(a) Marking Scheme (i) Group II/ 2 Because W has 2 electrons in its outer/ outermost shell/ W is magnesium (Mg) 1
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← Muon ← Is created when a neutrino collides and combines with an H2O proton (weak force) ← Creates blue light ← High energy; travels faster than the speed of light (in water) ← Neutrino ← Type of particle: Lepton (like electrons and muons) ← Most abundant particle in the universe ▪ 1016 neutrinos are passing through your body at any point in time ← Theoretically discovered by Wolfgang Pauli (1930); actually discovered in 1955 ← Produced during nuclear reaction or changes
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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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