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Atomic structure. ➢An atom consists of a nucleus composed of protons and neutrons and electrons which encircle the nucleus. ➢Protons and electrons have . PDF | On Apr 18, , Ramesh Duraisamy and others published Atomic Structure & Basic Concepts of Chemistry. Dalton's Atomic Theory (experiment based!) 3) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. E.g. CO2.

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Atomic Structure Pdf

CHEMISTRY. The rich diversity of chemical behaviour of different elements can be traced to the differences in the internal structure of atoms of these elements. CHAPTER 1 – ATOMIC STRUCTURE. 1. Atomic Structure. 1. The Atom; Protons, Neutrons, Electrons; Atomic Number; Elements; Atomic. Mass; Atomic Size. 1. Chapter 1 - Basic Concepts: atoms. Discovery of atomic structure. JJ Thomson (). Milliken (). Rutherford (). Rutherford ().

Some Basic Principles and Techniques. Atom is the smallest indivisible particle of the matter. Cathode ray discharge tube experiment: A cathode ray discharge tube madeof glass is taken with two electrodes. At very low pressure and high voltage,current starts flowing through a stream of particles moving in the tube fromcathode to anode. These rays were called cathode rays. When a perforatedanode was taken, the cathode rays struck the other end of the glass tube atthe fluorescent coating and a bright spot on the coating was developed. Cathode rays consist of negatively charged electrons. Cathode rays themselves are not visible but their behavior can be observed with help of fluorescent or phosphorescent materials. In absence of electrical or magnetic field cathode rays travel in straight linesd. The characteristics of the cathode rays do not depend upon the material of the electrodes and the nature of the gas present in the cathode ray tube. Charge to mass ratio of an electron was determined by Thomson.

Dalton estimated the atomic weights according to the mass ratios in which they combined, with the hydrogen atom taken as unity. However, Dalton did not conceive that with some elements atoms exist in molecules—e.

He also mistakenly believed that the simplest compound between any two elements is always one atom of each so he thought water was HO, not H2O. For instance, in he believed that oxygen atoms were 5. Adopting better data, in he concluded that the atomic weight of oxygen must actually be 7 rather than 5. Others at this time had already concluded that the oxygen atom must weigh 8 relative to hydrogen equals 1, if one assumes Dalton's formula for the water molecule HO , or 16 if one assumes the modern water formula H2O.

Avogadro had proposed that equal volumes of any two gases, at equal temperature and pressure, contain equal numbers of molecules in other words, the mass of a gas's particles does not affect the volume that it occupies.

For instance: since two liters of hydrogen will react with just one liter of oxygen to produce two liters of water vapor at constant pressure and temperature , it meant a single oxygen molecule splits in two in order to form two particles of water. Thus, Avogadro was able to offer more accurate estimates of the atomic mass of oxygen and various other elements, and made a clear distinction between molecules and atoms. Brownian Motion In , the British botanist Robert Brown observed that dust particles inside pollen grains floating in water constantly jiggled about for no apparent reason.

In , Albert Einstein theorized that this Brownian motion was caused by the water molecules continuously knocking the grains about, and developed a hypothetical mathematical model to describe it. Discovery of subatomic particles Main articles: Electron and Plum pudding model The cathode rays blue were emitted from the cathode, sharpened to a beam by the slits, then deflected as they passed between the two electrified plates.

Atoms were thought to be the smallest possible division of matter until when J. Thomson discovered the electron through his work on cathode rays. When a voltage is applied across the electrodes, cathode rays are generated, creating a glowing patch where they strike the glass at the opposite end of the tube.

Through experimentation, Thomson discovered that the rays could be deflected by an electric field in addition to magnetic fields , which was already known.

He concluded that these rays, rather than being a form of light, were composed of very light negatively charged particles he called " corpuscles " they would later be renamed electrons by other scientists. He measured the mass-to-charge ratio and discovered it was times smaller than that of hydrogen, the smallest atom. These corpuscles were a particle unlike any other previously known.

Thomson suggested that atoms were divisible, and that the corpuscles were their building blocks. Discovery of the nucleus Main article: Rutherford model The Geiger-Marsden experiment Left: Expected results: alpha particles passing through the plum pudding model of the atom with negligible deflection.

Right: Observed results: a small portion of the particles were deflected by the concentrated positive charge of the nucleus. Thomson's plum pudding model was disproved in by one of his former students, Ernest Rutherford , who discovered that most of the mass and positive charge of an atom is concentrated in a very small fraction of its volume, which he assumed to be at the very center. In the Geiger—Marsden experiment , Hans Geiger and Ernest Marsden colleagues of Rutherford working at his behest shot alpha particles at thin sheets of metal and measured their deflection through the use of a fluorescent screen.

To their astonishment, a small fraction of the alpha particles experienced heavy deflection.

Atomic structure pdf, Slides for Chemistry

Rutherford concluded that the positive charge of the atom must be concentrated in a very tiny volume to produce an electric field sufficiently intense to deflect the alpha particles so strongly. The first was the law of conservation of mass , closely associated with the work of Antoine Lavoisier , which states that the total mass in a chemical reaction remains constant that is, the reactants have the same mass as the products. First established by the French chemist Joseph Louis Proust in , [7] this law states that if a compound is broken down into its constituent chemical elements, then the masses of the constituents will always have the same proportions by weight, regardless of the quantity or source of the original substance.

John Dalton studied and expanded upon this previous work and defended a new idea, later known as the law of multiple proportions : if the same two elements can be combined to form a number of different compounds, then the ratios of the masses of the two elements in their various compounds will be represented by small whole numbers. For example, Proust had studied tin oxides and found that there is one type of tin oxide that is Dalton noted from these percentages that g of tin will combine either with Dalton found several examples of such instances of integral multiple combining proportions, and asserted that the pattern was a general one.

Most importantly, he noted that an atomic theory of matter could elegantly explain this law, as well as Proust's law of definite proportions. For example, in the case of Proust's tin oxides, one tin atom will combine with either one or two oxygen atoms to form either the first or the second oxide of tin. Indeed, carbon dioxide molecules CO2 are heavier and larger than nitrogen molecules N2.

Dalton proposed that each chemical element is composed of atoms of a single, unique type, and though they cannot be altered or destroyed by chemical means, they can combine to form more complex structures chemical compounds.

This marked the first truly scientific theory of the atom, since Dalton reached his conclusions by experimentation and examination of the results in an empirical fashion. In Dalton orally presented his first list of relative atomic weights for a number of substances.

This paper was published in , but he did not discuss there exactly how he obtained these figures. Dalton estimated the atomic weights according to the mass ratios in which they combined, with the hydrogen atom taken as unity. However, Dalton did not conceive that with some elements atoms exist in molecules—e. He also mistakenly believed that the simplest compound between any two elements is always one atom of each so he thought water was HO, not H2O.

For instance, in he believed that oxygen atoms were 5. Adopting better data, in he concluded that the atomic weight of oxygen must actually be 7 rather than 5.

Subatomic Medicine and the Atomic Theory of Disease

Others at this time had already concluded that the oxygen atom must weigh 8 relative to hydrogen equals 1, if one assumes Dalton's formula for the water molecule HO , or 16 if one assumes the modern water formula H2O. Avogadro had proposed that equal volumes of any two gases, at equal temperature and pressure, contain equal numbers of molecules in other words, the mass of a gas's particles does not affect the volume that it occupies.

For instance: since two liters of hydrogen will react with just one liter of oxygen to produce two liters of water vapor at constant pressure and temperature , it meant a single oxygen molecule splits in two in order to form two particles of water. Thus, Avogadro was able to offer more accurate estimates of the atomic mass of oxygen and various other elements, and made a clear distinction between molecules and atoms. Brownian Motion In , the British botanist Robert Brown observed that dust particles inside pollen grains floating in water constantly jiggled about for no apparent reason.

In , Albert Einstein theorized that this Brownian motion was caused by the water molecules continuously knocking the grains about, and developed a hypothetical mathematical model to describe it.

Discovery of subatomic particles Main articles: Electron and Plum pudding model The cathode rays blue were emitted from the cathode, sharpened to a beam by the slits, then deflected as they passed between the two electrified plates.

Atoms were thought to be the smallest possible division of matter until when J. Since some of the? Since only some of the? Strong deflections or even bouncing back of? This model explained that atom consists ofnucleus which is concentrated in a very small volume. The nucleus comprisesof protons and neutrons. The electrons revolve around the nucleus in fixedorbits. Electrons and nucleus are held together by electrostatic forces ofattraction.

atomic structure .pdf - CHE 108 Atomic Structure Worksheet...

Thus, b. According to electromagnetic theory of Maxwell, a charged particle undergoing acceleration should emitelectromagnetic radiation. Thus, an electron in an orbit should emitradiation. Thus, the orbit should shrink. But this does not happen. The model does not give any information about how electrons aredistributed around nucleus and what are energies of these electrons.

Is o t opes: These are the atoms of the same element having the same atomicnumber but different mass number. Isobars are the atoms of different elements having the same massnumber but different atomic number. These are those species which have the same numberof electrons. Electromagnetic radiations: The radiations which are associated withelectrical and magnetic fields are called electromagnetic radiations.

When anelectrically charged particle moves under acceleration, alternating electricaland magnetic fields are produced and transmitted.

[PDF] Subatomic Medicine and the Atomic Theory of Disease - Semantic Scholar

These fields aretransmitted in the form of waves. These waves are called electromagneticwaves or electromagnetic radiations. Oscillating electric and magnetic field are produced by oscillating charged particles.

These fields are perpendicular to each other and both areperpendicular to the direction of propagation of the wave. They do not need a medium to travel. That means they can even travel invacuum. It may be defined as the distance between two neighbouring crests or troughs of wave as shown.

It is denoted by?. It may be defined as the number of waves which passthrough a particular point in one second. Velocity v: It is defined as the distance travelled by a wave in onesecond. In vacuum all types of electromagnetic radiations travel with thesame velocity. It is denoted by v d. Wave number: Black body: An ideal body, which emits and absorbs all frequencies, is calleda black body. The radiation emitted by such a body is called black body radiation.

The phenomenon of ejection of electrons from thesurface of metal when light of suitable frequency strikes it is calledphotoelectric effect. The ejected electrons are called photoelectrons.

For each metal there is a characteristicminimum frequency below which photoelectric effect is not observed.

Thisis called threshold frequency. Photoelectric work function Wo: The minimum energy required to ejectelectrons is called photoelectric work function.

Energy of the ejected electrons: The light possesses both particle and wave like properties, i. Black body radiation and photoelectric effect Wave like properties are exhibited when it propagates interference an diffraction.

When a white light is passed through a prism, it splits into a series ofcoloured bands known as spectrum.

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It has bright lines with dark spaces between them.

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