Lesson number 49 Phenomena confirming complex structure atom. Radioactivity. Rutherford's scattering experiments a– particles. The composition of the atomic nucleus.
Lesson Objectives: introduce students to the nuclear model of the atom;
cultivate a conscientious attitude to learning, instill skills, how to independent work and work in a team;
to activate the thinking of schoolchildren, the ability to independently formulate conclusions, develop speech.
Lesson type: learning new materials.
Type of lesson: combined.
During the classes
Organizing time.
Updating students' knowledge.
Define the concept of x-rays.
properties of x-rays.
The use of x-rays.
Why do radiologists use gloves, aprons, glasses containing lead salts?
The short-wavelength limit of light perception in some people is 37∙10 -6 cm. Determine the frequency of oscillations in these waves. (8.11∙10 15 Hz),
Learning new material
The hypothesis that all substances are made up of a large number atoms, originated over two millennia ago. Supporters of the atomic theory considered the atom as the smallest indivisible particle and believed that the whole diversity of the world is nothing but a combination of immutable particles - atoms. Democritus position: "There is a division limit- atom". Aristotle's position: "The divisibility of matter is infinite."
Specific ideas about the structure of the atom developed as physics accumulated facts about the properties of matter. They discovered the electron, measured its mass and charge. The idea of the electronic structure of the atom, first expressed by W. Weber in 1896, was developed by L. Lorentz. It was he who created the electronic theory; electrons are part of an atom.
At the beginning of the century in physics there were very different and often fantastic ideas about the structure of the atom. For example, the rector of the University of Munich, Ferdinand Lindemann, stated in 1905 that "the oxygen atom is in the shape of a ring, and the sulfur atom is in the shape of a cake." Lord Kelvin's theory of the "vortex atom" continued to live, according to which the atom is arranged like smoke rings emitted from the mouth of an experienced smoker.
Based on discoveries, J. Thomson in 1898 proposed a model of an atom in the form of a positively charged ball with a radius of 10 -10 m, in which electrons "float" neutralizing positive charge. Most physicists were inclined to believe that J. Thomson was right.
However, in physics for more than 200 years, the rule has been adopted: the final choice between hypotheses can only be made by experiment. Such an experiment was set up in 1909 by Ernest Rutherford (1871-1937) with his collaborators.
Passing a beam of α-particles (charge + 2e, mass 6.64-1 (G 27 kg) through a thin gold foil, E. Rutherford found that some of the particles deviated by a rather significant angle from their original direction, and a small part α-particles are reflected from the foil.But, according to the Thomson model of the atom, these α-particles, when interacting with foil atoms, must deviate through small angles, on the order of 2 °.However, a simple calculation shows that in order to explain even such small deviations, one must assume that in atoms of the foil, a huge electric field tension over 200 kV/cm. There can be no such stresses in Thomson's polyethylene ball. Collisions with electrons don't count either. Indeed, in comparison with them, an α-particle flying at a speed of 20 km / s is the same as a cannonball with a pea.
In search of a clue, Rutherford suggested to Geiger and Marsden to check: "but can not α-particles bounce back from the foil."
Two years have passed. During this time, Geiger and Marsden counted more than a million scintillations and proved that about one α particle in 8 thousand is reflected back.
Rutherford showed that Thomson's model was in conflict with his experience. Summarizing the results of his experiments, Rutherford proposed a nuclear (planetary) model of the structure of the atom:
1. An atom has a nucleus, the size of which is small compared to the size of the atom itself.
2. Almost the entire mass of the atom is concentrated in the nucleus.
3. The negative charge of all electrons is distributed throughout the volume of the atom.
Calculations have shown that α-particles, which interact with electrons in matter, almost do not deviate. Only some alpha particles pass close to the nucleus and experience sharp deflections.
Physicists accepted Rutherford's message with restraint. For two years he himself also did not insist very strongly on his model, although he was confident in the infallibility of the experiments that led to it. The reason was the following.
According to electrodynamics, such a system cannot exist, since an electron rotating according to its laws will inevitably and very soon fall into the nucleus. I had to choose: either electrodynamics or the planetary model of the atom. Physicists have silently chosen the former. Silently, because it was impossible to either forget or disprove Rutherford's experiments. The physics of the atom has come to a standstill.
The total charge of the electrons is equal to the charge of the nucleus, taken with a minus sign.
The total number of protons and neutrons in the nucleus is called the mass number - A.
The mass of a proton is 1840 times the mass of an electron.
z is the nuclear charge. Mass number A = Z+N.
The number of neutrons in the nucleus: N = A-Z.
In the nuclei of the same chemical element, the number of neutrons can be different, while the number of protons is always the same.
Different kinds of the same element that differ in the number of neutrons in the nucleus are called isotopes.
III. Fixing the material
What is the essence of the Thomson model?
Draw and explain the scheme of Rutherford's experiment on scattering - α particles. What do we see in this experience?
Explain the reason for the scattering of α-particles by atoms of matter?
What is the essence of the planetary model of the atom?
Determine the composition of the nuclei of silver, mendelevium, cobalt.
IV. Summing up the lesson
§52-53. Exercise 42
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1 min British = 0.0160126656733981 drachma
Initial value
Converted value
cubic meter cubic kilometer cubic decimeter cubic centimeter cubic millimeter liter exalitre petaliter teraliter gigaliter megaliter kiloliter hectoliter decalitre deciliter centiliter milliliter microliter nanoliter picoliter femtoliter attoliter cc drop barrel (petroleum) barrel US barrel British gallon US pint US British quart US quart English glass American glass (metric) glass British ounce fluid US ounce fluid British tablespoon Amer. tablespoon (meter) tablespoon UK dessert spoon amer. dessert spoon Brit. teaspoon amer. metric teaspoon teaspoon Brit. gill, gill american gill, gill british minim american minim british cubic mile cubic yard cubic foot cubic inch reg ton 100 cubic feet 100 cu. foot drachma cor (biblical unit) homer (biblical unit) baht (biblical unit) gyn (biblical unit) cab (biblical unit) log (biblical unit) glass (Spanish) volume of the Earth Planck volume cubic astronomical unit cubic parsec cubic kiloparsec cubic megaparsec cubic gigaparsec barrel bucket shtof quarter wine bottle vodka bottle glass cup shkalik
Electric potential and voltage
Learn more about volume and units of measurement in recipes
General information
Volume is the space occupied by a substance or object. Also, the volume can denote the free space inside the container. Volume is a three-dimensional quantity, unlike, for example, length, which is two-dimensional. Therefore, the volume of flat or two-dimensional objects is zero.
Volume units
Cubic meter
The SI unit for volume is the cubic meter. The standard definition of one cubic meter is the volume of a cube with edges one meter long. Derived units such as cubic centimeters are also widely used.
Liter
The liter is one of the most commonly used units in the metric system. It is equal to the volume of a cube with edges 10 cm long:
1 liter = 10 cm × 10 cm × 10 cm = 1000 cubic centimeters
It's like 0.001 cubic meters. The mass of one liter of water at 4°C is approximately equal to one kilogram. Often milliliters are also used, equal to one cubic centimeter or 1/1000 of a liter. A milliliter is usually referred to as ml.
Jill
Gills are units of volume used in the United States to measure alcoholic beverages. One gill is five fluid ounces in the British imperial system, or four in the US. One American jill is equal to a quarter pint or half a cup. In Irish pubs, strong drinks are served in portions of a quarter of a jill, or 35.5 milliliters. The Scottish portions are smaller - one-fifth of a jill, or 28.4 milliliters. In England, until recently, servings were even smaller, only one-sixth of a jill or 23.7 milliliters. Now, it's 25 or 35 milliliters, depending on the rules of the institution. The hosts can decide for themselves which of the two servings to serve.
AMD
Dram, or drachma - a measure of volume, mass, as well as a coin. In the past, this measure was used in the pharmacy business and was equal to one teaspoon. Later, the standard volume of a teaspoon changed, and one spoon became equal to 1 and 1/3 drachmas.
Volumes in cooking
Liquids in cooking recipes are usually measured by volume. Bulk and dry products in the metric system, on the contrary, are measured by weight.
Tea spoon
The volume of a teaspoon varies different systems measurements. Initially, one teaspoon was a quarter of a tablespoon, then one third. It is the latter volume that is now used in American system measurements. This is approximately 4.93 milliliters. In American dietetics, the size of a teaspoon is 5 milliliters. In the UK it is common practice to use 5.9 milliliters, but some dietary guides and cookbooks use 5 milliliters. The volume of a teaspoon used in cooking is usually standardized in each country, but different sizes of spoons are used for eating.
Tablespoon
The volume of a tablespoon also varies depending on the geographic region. So, for example, in America, one tablespoon is three teaspoons, half an ounce, about 14.7 milliliters, or 1/16 of an American cup. Tablespoons in the UK, Canada, Japan, South Africa and New Zealand also contain three teaspoons. So, a metric tablespoon is 15 milliliters. A British tablespoon is 17.7 milliliters if a teaspoon is 5.9, and 15 if a teaspoon is 5 milliliters. Australian tablespoon - ⅔ ounce, 4 teaspoons, or 20 milliliters.
Cup
As a measure of volume, a cup is not as strictly defined as spoons. The volume of the cup can vary from 200 to 250 milliliters. A metric cup is 250 milliliters, while an American cup is slightly smaller, about 236.6 milliliters. In American dietetics, the volume of a cup is 240 milliliters. In Japan, cups are even smaller - only 200 milliliters.
Quarts and gallons
Gallons and quarts also have different size, depending on the geographic region where they are used. In the imperial system of measurement, one gallon is equal to 4.55 liters, and in the American system of measurements - 3.79 liters. Fuel is generally measured in gallons. A quart is equal to a quarter of a gallon and, respectively, 1.1 liters in the American system, and approximately 1.14 liters in the imperial system.
Pint
Pints are used to measure beer even in countries where pints are not used to measure other liquids. In the UK, pints are used to measure milk and cider. A pint is equal to one eighth of a gallon. Some other countries in the Commonwealth and Europe also use pints, but since they depend on the definition of the gallon, and the gallon has a different volume depending on the country, pints are also not the same everywhere. An imperial pint is approximately 568.2 milliliters, while an American pint is 473.2 milliliters.
Fluid ounce
An imperial ounce is approximately equal to 0.96 US ounce. Thus, an imperial ounce contains approximately 28.4 milliliters, and an American ounce contains 29.6 milliliters. One US ounce is also approximately equal to six teaspoons, two tablespoons, and one eighth cup.
Volume calculation
Liquid displacement method
The volume of an object can be calculated using the liquid displacement method. To do this, it is lowered into a liquid of a known volume, a new volume is geometrically calculated or measured, and the difference between these two values is the volume of the measured object. For example, if, when an object is lowered into a cup with one liter of water, the volume of liquid increases to two liters, then the volume of the object is one liter. In this way, only the volume of objects that do not absorb liquid can be calculated.
Formulas for calculating volume
Volume geometric shapes can be calculated using the following formulas:
Prism: the product of the area of the base of the prism and the height.
Rectangular parallelepiped: product of length, width and height.
Cube: edge length to the third power.
Ellipsoid: product of semiaxes and 4/3π.
Pyramid: one third of the product of the area of the base of the pyramid and the height. Post a question to TCTerms and within a few minutes you will receive an answer.
