AtomicStructureSwanshurstSchool：原子结构swanshurst学校26张课件

1、Atomic StructureUnit 1: Chemistry and Our Earth第1页，共26页。Teachers notes included in the Notes PageFlash activity (these activities are not editable)Accompanying worksheetPLTSFor more detailed instructions, see the Getting Started presentation第2页，共26页。What is an atom?An atom is the smallest particle t

2、hat can exist on its own. Atoms are tiny. A single atom is about 0.00000001 cm wide. Gold is an element made up of only gold atoms.In the late 20th century, electron microscopes were invented. These very powerful microscopes have allowed scientists to look at atoms. 第3页，共26页。The structure of an atom

3、An atom is made of smaller particles known as subatomic particles. These particles cannot exist on their own.Electrons are negatively charged particles spread around the edge of the atom. The centre of the atom is called the nucleus. It is composed of two different types of particles called nucleons

4、. Protons are nucleons with a positive charge.Neutrons are uncharged nucleons.第4页，共26页。Label the atom第5页，共26页。How was atomic structure discovered?第6页，共26页。Mass and electrical chargeThere are two properties of protons, neutrons and electrons that are especially important:masselectrical charge.The ato

5、ms of an element contain equal numbers of protons and electrons and so have no overall charge.-1almost 001+11electronneutronprotonChargeMassParticle第7页，共26页。Properties of subatomic particles第8页，共26页。In 1989, an IBM researcher called Don Eigler created the IBM logo out of 35 individual xenon atoms.Th

6、is was the birth of nanotechnology, with the idea that devices could be built atom by atom. IBM have now used gold atoms to store information, and trapped carbon monoxide to use in computer circuits.The atoms were individually moved with a scanning tunnelling microscope. You cannot see the atoms mov

7、e, but you see a before and after image.Case study: art and atoms第9页，共26页。第10页，共26页。IsotopesSome elements like carbon are made up of a mixture of isotopes. Isotopes of an element have the same number of protons and electrons but a different number of neutrons.Isotopes have the same chemical properti

8、es because they have the same number of protons. However, isotopes have different physical properties because they have different masses. The number of protons determines the type of element.第11页，共26页。Carbon isotopes第12页，共26页。Objects found at an archaeological dig can be difficult to date. If the ob

9、jects were once living, radiocarbon dating can be used.Living organisms take up carbon, including radioactive carbon-14. Case study: radiocarbon dating By measuring the proportion of carbon-14 remaining in a sample, its age can be estimated.Carbon-14 decays at a predictable rate. Once an organism di

10、es, they stop taking up carbon and the amount declines.第13页，共26页。Isotopes of hydrogen There are three isotopes of hydrogen. 99.98% of naturally-occurring hydrogen is hydrogen-1.1 proton0 neutrons1 electronhydrogen1 proton1 neutrons1 electrondeuterium1 proton2 neutrons1 electrontritium第14页，共26页。Isoto

11、pes: true or false?第15页，共26页。Radioactive isotopes can be used as tracers in the body to produce images of some organs. For example, iodine is used by the thyroid gland in the neck to make hormones. Case study: imagingRadioactive iodine-131 or iodine-123 can be used to check that the thyroid gland is

12、 functioning properly. It is given to the patient as a capsule to swallow. The isotope emits radiation as it passes through the body. Its path can be detected by a Geiger counter or other device. The rate and location of iodine uptake can indicate how well the thyroid gland is functioning.第16页，共26页。

13、第17页，共26页。How are electrons arranged?Electrons are not evenly spread but exist in layers called shells. (The shells can also be called energy levels). The arrangement of electrons in these shells is often called the electron configuration.Note that this diagram is not drawn to scale the atom is most

14、ly empty space. If the electron shells were the size shown, the nucleus would be too small to see.1st shell2nd shell3rd shell第18页，共26页。Electron arrangementEach shell has a maximum number of electrons that it can hold. Electrons will fill the shells nearest the nucleus first.1st shell holdsa maximum

15、of2 electrons2nd shell holdsa maximum of8 electrons3rd shell holdsa maximum of8 electronsThis electron arrangement is written as 2,8,8. 第19页，共26页。Complete the electron configurations第20页，共26页。Electron trends in the periodic tableDown a group:The point at which a new period starts is the point at whi

16、ch electrons begin to fill a new shell.The number of a group is the same as the number of electrons in the outer shell of elements in that group, except for group 0.the number of outer shell electrons is the same;the number of complete electron shells increases by one.the number of outer shell elect

17、rons increases by one;Across a period:the number of complete electron shells stays the same.The periodic table displays trends in electron configurations.第21页，共26页。Groups and periods第22页，共26页。Using electronic structureGroup 0 elements are also known as the noble gases. They have a full outer shell o

18、f electrons and do not easily undergo chemical reactions.Scientists can use their knowledge of electronic structure to predict elements that might react with group 0 elements.In 1933, Linus Pauling predicted that xenon could form a compound with fluorine. Fluorine is a very reactive element in group 7 of the periodic table.However, it wasnt until 1962 that Howard Claasen ma