無(wú)機(jī)化學(xué)課件：02 Atoms

1、Chemistry: Atoms FirstJulia Burdge & Jason OverbyCopyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Chapter 2Atoms and thePeriodic TableAtoms and the Periodic Table22.1 Atoms First2.2Subatomic Particles and Atomic StructureDiscovery of the ElectronRadioacti

2、vityThe Proton and the Nuclear Model of the AtomThe Neutron2.3Atomic Number, Mass Number, and Isotopes2.4 Average Atomic Mass2.5 The Periodic Table2.6 The Mole and Molar MassThe MoleMolar MassInterconverting Mass, Moles, and Numbers of Atoms Atoms FirstAn atom is the smallest quantity of matter that

3、 still retains the properties of matter.An element is a substance that cannot be broken down into two or more simpler substances by any means.Examples: gold, oxygen, helium2.1Once a single atom has been obtained, dividing it smaller produces subatomic particles.The nature, number, and arrangement of

4、 subatomic particles determine the properties of atoms, which in turn determine the properties of all things material.Subatomic Particles and Atomic StructureIn the late 1800s, many scientists were doing research involving radiation, the emission and transmission of energy in the form of waves.They

5、commonly used a cathode ray tube, which consists of two metal plates sealed inside a glass tube from which most of the air has been evacuated.2.2Subatomic Particles and Atomic StructureWhen metal plates are connected to a high-voltage source, the negatively charged plate, or cathode, emits an invisi

6、ble ray.The cathode ray is drawn to the anode where it passes through a small hole.Although invisible, the path is revealed when the ray strikes a phosphor-coated surface producing a bright light.Subatomic Particles and Atomic StructureResearches discovered that like charges repel each other, and op

7、posite charges attract one another.J. J. Thomson (1856-1940) noted the rays were repelled by a plate bearing a negative charge, and attracted to a plate bearing a positive charge.Subatomic Particles and Atomic StructureThis prompted him to propose the rays were actually a stream of negatively charge

8、d particles.These negatively charged particles are called electrons.By varying the electric field and measuring the degree of deflection of cathode rays, Thomson determined the charge-to-mass ratio of electrons to be 1.76108 C/g. (C is coulomb, the derived SI unit of electric charge.)Subatomic Parti

9、cles and Atomic StructureR. A. Millikan (1868-1953) determined the charge on an electron by examining the motion of tiny oil drops.The charge was determined to be -1.602210-19 C.Subatomic Particles and Atomic StructureKnowing the charge, he was then able to use Thomsons charge-to-mass ratio to deter

10、mine the mass of an electron.Subatomic Particles and Atomic StructureWilhelm Rontgen (1845-1923) discovered X-rays. They were not deflected by magnetic or electric fields, so they could not consist of charged particles.Antoine Becquerel (1852-1908) discovered radioactivity, the spontaneous emission

11、of radiation.Radioactive substances, such as uranium, can produce three types of radiation.Subatomic Particles and Atomic StructureAlpha () rays consist of positively charged particles, called particles.Beta () rays, or particles, are electrons so they are deflected away from the negatively charged

12、plate.Gamma () rays, like X-rays, have no charge and are unaffected by external electric or magnetic fields.Subatomic Particles and Atomic StructureErnest Rutherford used particles to prove the structure of atoms.The majority of particles penetrated the gold foil undeflected.Sometimes, particles wer

13、e deflected at a large angle.Sometimes, particles bounced back in the direction from which they had come.Rutherford proposed a new model for the atom:Positive charge is concentrated in the nucleus.The nucleus accounts for most of an atoms mass and is an extremely dense central core within the atom.A

14、 typical atomic radius is about 100 pmA typical nucleus has a radius of about 5103 pm1 pm = 11012 mSubatomic Particles and Atomic StructureProtons are positively charged particles found in the nucleus.Neutrons are electronically neutral particles found in the nucleus.Neutrons are slightly larger tha

15、n protons.Subatomic Particles and Atomic StructureAtomic Number, Mass Number, and IsotopesElemental symbolAll atoms can be identified by the number of protons and neutrons they contain.The atomic number (Z) is the number of protons in the nucleus.Atoms are neutral, so its also the number of electron

16、s.Protons determine the identity of an element. For example, nitrogens atomic number is 7, so every nitrogen has 7 protons.The mass number (A) is the total number of protons and neutrons.Protons and neutrons are collectively referred to as nucleons.Mass number(number of protons + neutrons)Atomic num

17、ber(number of protons)2.3Atomic Number, Mass Number, and IsotopesMost elements have two or more isotopes, atoms that have the same atomic number (Z) but different mass numbers (A).1 proton0 neutrons1 proton1 neutron1 proton2 neutronsIsotopes of the same element exhibit similar chemical properties, f

18、orming the same types of compounds and displaying similar reactivities.Average Atomic Mass2.4Atomic mass is the mass of an atom in atomic mass units (amu).1 amu = 1/12 the mass of a carbon-12 atomThe average atomic mass on the periodic table represents the average mass of the naturally occurring mix

19、ture of isotopes.Average mass (C) = (0.9893)(12.00000 amu) + (0.0107)(13.003355 amu) IsotopeIsotopic mass (amu)Natural abundance (%)12C12.0000098.9313C13.0033551.07= 12.01 amuThe Periodic TableThe periodic table is a chart in which elements having similar chemical and physical properties are grouped

20、 together.2.5The Periodic TableElements are arranged in periods, horizontal rows, in order of increasing atomic number.The Periodic TableElements can be categorized as metals, nonmetals, or metalloids.Metals are good conductorsof heat and electricity.Nonmetals are poorconductors of heat orelectricit

21、y.Metalloids haveintermediate properties.The Periodic TableA vertical column is known as a group.The Periodic TableGroup 1A elements (Li, Na, K, Rb, Cs, Fr) are called alkali metals.The Periodic TableGroup 2A elements (Be, Mg, Ca, Sr, Ba, Ra) are called alkaline earth metals.The Periodic TableGroup

22、6A elements (O, S, Se, Te, Po) are called chalcogens.The Periodic TableGroup 7A elements (F, Cl, Br, I, At) are called halogens.The Periodic TableGroup 8A elements (He, Ne, Ar, Kr, Xe, Rn) are called the noble gases.The Periodic TableGroups 1B and 3B-8B are called the transition elements or transiti

23、on metals.The Mole and Molar MassThe mole is defined as the amount of a substance that contains as many elementary entities as there are atoms in exactly 12 g of carbon-12.This experimentally determined number is called Avogadros number (NA).We normally round this to 6.0221023.1 mole = 6.0221023, just like 1 dozen = 12 or 1 gross = 144.NA = 6.0221415 x 10232.6The MoleOne mole each of some familiar substances:AluminumCopperWaterSalt (Sodium Chloride)Sugar (Sucrose)Helium (in balloon)Molar MassThe molar mass of a su