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can be traced to the differences in the internal structure of atoms of these elements. UNIT 2. STRUCTURE OF ATOM. After studying this unit you will be able to. Atomic structure. ➢An atom consists of a nucleus composed of protons and neutrons and electrons which encircle the nucleus. ➢Protons and electrons have . Chemistry Notes for Class 11 STRUCTURE OF ATOM Download in pdf. Atom is the smallest indivisible particle of the matter. Atom is made of electron, proton.

Structure Of Atom Pdf

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Sizing up the Atom. ▫ Elements are able to be subdivided into smaller and smaller particles – these are the atoms, and they still have properties of that element. PDF | On Apr 18, , Ramesh Duraisamy and others published Atomic Structure & Basic Concepts of Chemistry. 2 THE STRUCTURE OF ATOMS. The remarkable advancement of science in the first half of the 20th century was characterized by parallel developments in.

Hg Salt 2. Iron 7. Silver The term specific gravity denotes the ratio of the. Usually, the reference substance for. Density of substance. Density of reference substance. Specific gravity, being the ratio of two densities, has. Usually the specific gravity of any. Mass g. Volume 45 cm. Density of sample. Density of water. The de nsity of water at Because gasoline has a specific gravity of 0.

Conversion of The SI unit of leng th is the m eter m and the SI. Generally, chemists work with smaller volumes,. Another common unit of volume is the liter L. One liter volume is equal to mL or cm. Usually, number of atoms is measured in the units of.

This unit called one mole of atoms. T he number of atoms in one mole of any. For example, let us. Cl atoms. This would be a produce 6. If we can determine number of carbon atoms. One mole of C atoms,. C atoms; 0. A single CCl. Because we have 3x The chemistry deals the study of matter and the. Matter is anything that. Thus, e verything in. All substances, at least in principle, can exist in. The gases differ. In a solid, molecules are held close. Molecules in a liquid are close together but.

In a gas, distances that are large. The three states of matter can be interconverted. Upon heating, a solid ice will melt to form a liquid.

Fur ther heating. On the. When the liquid is cooled further, it. Mass and Weight,. Physical and Chemical properties, Atoms and. Substances are identified by their properties as well. Color, melting point, and boiling. A physical prop erty. Water differs. Therefore, the melting point. On the other hand the statement. After the change, the. In the case, of water we cannot. All measurable properties of matter fall into one of. The measured value of an.

Mass, which is the quantity of. More matter means more mass. Values of the same extensive property can be added.

For example, two copper pennies will have. The value of an extensive quantity. The m easured value of an intensive property does. Density, defined as the mass of an object divided by. We consider the. Suppose that we have two beakers of. If we combine them. Unlike mass, length, and volume, temperature and. An atom is t he smallest particle of an element that. The word. John Dalton, an English chemist.

A molec ule i s the smallest particle of an element or.

A molecule may consist of a single atom,. Water has a def inite composition. Each water.

CBSE Guide Structure of Atom class 11 Notes

Subdivision of a water. A substance is a form of m atter that has a definite. Examples are water, ammonia, sucrose, gold and. Substances differ from one another in. A mixture is a combination of two or more.

S ome familiar examples are air ,. Mixtures do not have. Mixtures are either homogeneous or heterogeneous. When a spoonful of sugar dissolves in water we. If sand is mixed with iron f ilings, however, the sand.

This type. Any mixture, whether homogeneous or. Condensing the vapor will give us back the water. An element is a substance that cannot be separated. To date,. Eighty-three of them oc cur naturally on Earth. Scientists via nuclear processes have created the. Only a few elements, such as the gases helium,. Other eleme nts, such as the gases nitrogen,. The element. For convenience, chemists use symbols of one or. The first letter. For example, Co is the symbol for the. Names and symbols of.

Name Symbol Name Symbol. Aluminum Al Fluorine F. Oxygen O Arseni c As. Gold Au Phosphorus P. Barium Ba Hydrogen H.

Platinum Pt Bismuth Bi. Iodine I Potassium K. Bromine Br Iron Fe. Silicon Si Calcium Ca. Lead Pb Silver Ag. Carbon C Magnesium Mg. Sodium Na Chlorine Cl. Manganese Mn Sulfur S. Chromium Cr Mercury Hg. Tin Sn Cobalt Co. Nickel Ni Tungsten W.

Copper Cu Nitrogen N. Zinc Zn. The symbols of some el ements are derived from. Atoms of most elements can interact with one. For example, hydrogen. Water is made up of two parts. Thus, water is a.

Out of all the elements, only the six noble gases He,. Ne, Ar, Kr,Xe, and Rn exist in nature as single. F or this reason , they are c alled mon atomic. Most matter is. A molecule is formed from least two atoms in a. A molecule may. Thus, a molecule is not necessarily a compound,. On the other hand, water is a molecular compound.

H atoms and one O atom. Like atoms, molecules are.

Other elements that normally exist as. A diatomic molecule. The v ast m ajority of mol ecules contain mor e than. They can be atoms of the same element,. Molecules containing more than. O and ammonia NH. An ion is an atom or a group of atoms that has a net. The loss of one or more.

For example, a sodium atom Na. Na atom: An anion is an ion whose net charge is negative due. A chlorine. Cl atom: Sodium chloride NaCl , table salt, is an ionic.

An atom can lose or gain more than one. The ions Na. Examples of ions formed by the loss or gain m ore. Polyatomic ions such as OH.

Except when all the numbers involved are integers,. For this reason, it is. We must always be careful in scientific work to. Thus Thus m contains three significant figures,.

Their purpose is to indicate the. For example,. Thus 2. If a number is less than 1, the n only the zeros that. Thus cm may have one significant figure the. We cannot know which. In this particular.

The fol lowing example shows the determination. We follow the rules for determining. Three d Two e Four f This is an. The number of significant figures. A second set of rules specifies how to handle. The rounding off procedure is as follows, to. Thus, 8. If the first. Thus 8. If an object has a mass of. We do not round off this product to one significant. Similarly, to take the average o f the two measured. Because the number 2 is 2. In fifth century, the Gree k philosopher Democritus.

Experimental evidence from early. It w as in. Acc ording to this. Elements are composed of extremely small. All atoms of a given. The atoms of one. Compounds are composed of atoms of more than. In any compound, the ratio of the. A chemical reaction involves only the separation,. It states that atoms of one element are. D alton. But he did realize that the. The 2.

This idea is an e xtension of law. According to. It is another way of sta ting the law of. Sinc e matter is made. However, a series of investigations,.

This research discovered the three such. One device used to investigate the atomic struc ture. When the two. The cathode ray is drawn to the. When the ray strikes the. In some e xperiments two electrically charged plates. When the magnetic field is on and. When only the electric field is on, the ray strikes. W hen both magnetic and the electric fields. According to electromagnetic theory, a. Since the cathode ray is attracted by. We know these. An English physics, J.

Thomson, used a catho de. The number he came. Thereafter, in a. His work proved that. In his experiment, he suspended the charged drops. Using his knowledge. From these data he. The German physicist Wilhelm Rontgen noticed in. This hi ghly energetic. Since a mag net could not. Rontgen called them X. Like X rays, the rays from the. One of. Since t hen, any element emits the radiation as.

Three types of rays are produced by the decay, or. Two of the three are deflected by. The third type of. By the early s, two features of atoms had. To maintain electric neutrality,. Therefore, Thomson proposed. The New Zealand physicist Ernest Rutherford,. Rutherford carried out a series of. He was observed that the majority of particles. Rutherford, explained the results of the.

Acc ording to Rutherford concept, most of. This explains why. The atoms have. The positively charged. It was known that. Therefore, the ratio of the mass of a helium. Rutherford and. English physicist, James Chadwick, provided the. When Chadwick bombarded a thin sheet of. Later experiments showed that the rays actually.

The number of protons and neutrons they contain. The atomic number Z is the. In a neutral atom the number of protons is. For example, the atomic number. This means that each neutral. The mass number A is the total number of protons. Except for the most common form of. The number of neutrons in a n atom is equal to the. For example, the mass number of.

Thus the number of neutrons. The atomic. The a ccepted way t o denote the atomic number and.

Most of the elements have two or more isotopes;. For example, there are three. One, simply known a s. Thus, for the isotope of hydrogen, we. As another example, consider two. Earliest view of light du e to Newton regarded light. This is due to. But it is. Hygens proposed wave like character of light. In James Clark Maxwell proposed. These waves have. These consist of electric and ma gnetic fields that.

The velocity equal to that of light,. These electromagnetic radiations donot require. Each element has a characteristic line spectrum. The spectra can be used to identify ele ments. This spectrum of each element was characterized.

A familiar example of a electromagnetic waves like. The waves originate. That is, if we drop a stone into one end of qu iet. This up-. A wave is a c ontinuously repeati ng change or. Light is also. Visible light, X rays and radio waves all are th e. The point of. Thus, waves may be considered as a continuous.

A wave was characterized by its wavelength and. SI unit: In following figure shows the frequency corresponds. The frequency is expressed in the unit of. Amplit ude: It is the vertical distance from the.

Height of. Velocity C: Distance travelled by a light in one. The number of waves per unit. There are many kinds of waves, such as. A ccording to. These two components have the same. Electromagnetic radiation is the emission and. Violet Red. The fig. The range of. The motions of electrons within atoms and. The shortest waves, which also have the highest.

In fig. Beyond these e xtremes,. IR radiation has wavelengths greater. Issac Newton, who studied the properties of light in. In , British physicist Thomas. Young showed that light like waves could be. By the early part of the twentieth century, the wave. But i n. Max Planck found a theoretical f ormula that. According to Planck, the atoms of the solid. Radiant energy is not emitted or absorbed. In the case of light, the quanta o f energy are.

The amount of ene rgy associated with a.

This relation found to be valid for all type of. The total am ount of energy emitted or absorbed. This means that a body can e mit or absorb. O r any. But cannot emit or. Equations 1 and 2 give the relation between. A radiation which has higher the frequency or. Einstein used this photon concept to explain the.

The phot oelectric e ffect is the ejection of electrons. Electrons are ejected, only. For example, violet light wil l cause potassium metal. The photon cease to exist as a. The wave and particle pictures of light should be. When white light from Sun is passed through a prism,. This means that Sunlight is. The splitting of light.

In this. Unlike the spectrum obtained by analyzing the. The spectrum of atoms consists of sharp well-defined. There a re two types of atomic spectra. Emission spectra are obtained when the radiations. When the gases or vapor of ch emical substances. The color of light depends upon the. Example, sodium. This type of spectrum consists of sharp well-. Such spectrum is. The line spectrum also known a s a tomic spectrum. Each element gives a unique spectrum irrespective.

Sodium always gives line s at nm and From this reason line spectra are also.

When a continuous electromagnetic radiation. We obtain a spectrum in which dark. T hese da rk l ines indicate that. Such a spectrum containing few dark li nes due to. The d ark lines of wavelengths are also. Example, absorption of. Na consists of lines at nm and The spectrum of hydrogen atom has played a very.

The spectrum of hydrogen atom can be. The emitted light radiation is analyzed by. The spectrum consists of large. In , J. Balmer developed a relationship among. These series of l ines which app ear in visible region. Afterwards, a series of spectral lines o f H. These series of.

As the other series of h ydrogen spectral lines were. Rydberg, a nd is known a s Rydberg equation derived. The energy levels of the electron in the hy drogen. The difference between the e nergies of the. Because this transition results in the emission of a. When a photon is emitted, n. If when energy is absorbed, n. The brightness of a spectral line depends on how.

In equation 3 by substituting R. The emission spectrum of hydrogen includes a. Lyman 1 2,3,4,…… Ultra violet.

Balmer 2 3,4,5,…… Visible and UV. Paschen 3 4,5,6,…….

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Brackett 4 5,6,7,……. Pfund 5 6,7,8,……. The above equation 3 , and lines only applicable. But other atoms lines are. The spectrum of hydrogen atom holds the key to.

Bohr proposed the. An a tom consists of a massive positively. The electrons re volving. These non-radiating. Each orbit is at different distance from the.

Hence, stationary states also. The energy associated with different energy levels. The letters of orbit shell: Energy associated with an energy level is giv en by.

Different energy levels are not equally spaced. It goes on decreasing. Angular momentum of an electron is a whole. The velocity of electron in n. Because of electron transition between two. Since en ergy cannot be lost continuously, and. Such a state. On gaining ene rgy from an external source. However the excited state is unstable, and. This acc ounts for the spectral lines in. It i s applicable only to hydrogen atom or.

The spectra of multi electron system cannot be. The experimental value of ionization energy. Bohr Theory cannot explain the mode of. It gives the flat model of the orbit. By using spectroscope of high resolving power,.

This goes against the modern ideas of. De Broglie stated that if light waves can behave. He argued that if an electron does behave lik e a. The relation between the circumference of an allowed. So, energy of. Thus, the waves can behave like particles and. So, De. Broglie deduced that the pa rticle and wave properties.

Note that the left side of equation. Calculate the de-Broglie wavelength of a ball of.

He did not explain why. Describe the proble m of trying to locate a subatomic. It stat ed that it is impossible to know simultaneously.

It is stated mathematically,. Applying Heisenberg unce rtainty principle to the. H atom, we see that in reality the electron does not. If it di d, we could determine precisely the position. Uncertainty principle and idea of probability. But uncertainty. This new approach called. In Erwin Schrodinger Austrian physicist.

In general the Schrodinger equation requires. According to wave theory, the intensity of light is. The most likely to find a photon is. The Schrodinger equation specifies the possible. These energy states and wave. In quantum me chanics, concept of elec tron density.

According to quantum mechanics, an atomic orbital. When we say that an electron is in a certai n. Therefore, an atomic. The Schrodinger equation is applicable nicely for the. So, chemists and.

So, they. In quantum mechanics, three quantum numbers are. These numbers a re derived f rom the. They are called the principal.

These qua ntum numbers will be us ed t o desc ribe. A fourt h. The principal quantum number n can have. In the case of. For other. The size of an atom also depends on the value of. Shells are. This quantum number distinguishes t he orbitals of. The values. With each shell of quantum number, n, there are. An electron has a n value is 3, the possible value. We denote a sub-shell with a particular shell, we. For example, 2p d enotes a sub-shell with quantum. The magnetic quantum number m.

Within a sub-shell,. The allowed values. The orbitals have. In addition each orbital of a given sub-shell has the. According to ele ctromagnetic theory, a spinning. The following figure shows the two possible. It is necessary to. The following table shows the relation between.

Relation between quantum numbers and. Atomic orbital Designations. We know that, E. Thus the energies of hydrogen orbital. The 1s orbital in a.

An electron residing in. An electron i n the. The energy picture is more complex for many-. The e nergy of an. Due to the repulsion. The increasing order of the orbital as follows,. By using the four quantum numbers n, l,m. It is convenient to write out all the.

For example, above, their quantum numbers are.

The value of. In the case of hydrogen atom, contains only one. The electron may be in the 1s orbital. For many. We can formulate some general rules for. For example, if. Therefore, the maximum number of. The following example illustra tes the procedure to.

Structure of atom: Discovery of electrons, protons and neutrons

What is the maximum number of electrons that. The number of orbitals. Since each. Electronic configuration is expressed by indicating. For example, in ground state hydrogen atom must be. A box for an orbital square or c ircular an arrow. Example, electron. In the g round state electronic configuration of an.

Thus, an orbital wit h lowest energy will. In the case of many electron systems we can use. It state s that no electrons in an. If two electrons m ay occupy in the same. For example we consider the. The orbital diagram. C atom. The fact that carbon atoms are paramagnetic, each. Similarly the electronic. N atom. F atom. Based on the a bove rules the electronic configuration. 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. It has bright lines with dark spaces between them. Electromagnetic spectrum is a continuous spectrum.

It consists of a range ofelectromagnetic radiations arranged in the order of increasing wavelengths ordecreasing frequencies. It extends from radio waves to gamma rays. The spectrum of radiationemitted by a substance that has absorbed energy is called an emissionspectrum. The wavelengths which are absorbed are missing and comeas dark lines. The study of emission or absorption spectra is referred as spectroscopy.

An electron in the hydrogen atom can move around the nucleus in a circular path of fixed radius and energy. These paths are called orbits orenergy levels. These orbits are arranged concentrically around thenucleus b. As long as an electron remains in a particular orbit, it does not lose or gain energy and its energy remains constant. When transition occurs between two stationary states that differ inenergy, the frequency of the radiation absorbed or emitted can be calculated.

It states that it is impossible to determine simultaneously, the exact position and exact momentum or velocity of an electron. Classical mechanics: It successfullydescribes the motion of macroscopic particles but fails in the case ofmicroscopic particles. Quantum mechanics is a theoretical science that deals with the study of themotions of the microscopic objects that have both observable wave like andparticle like properties.

Quantum mechanics is based on a fundamental equation which is calledSchrodinger equation. Probability density: The value of?

It is called probability density. The region of space around the nucleus where the probability offinding an electron is maximum is called an orbital.

There are a set of four quantum numbers which specifythe energy, size, shape and orientation of an orbital. To specify an orbital only three quantum numbers are required whileto specify an electron all four quantum numbers are required.

P r incipal quantum number n: It identifies shell, determines sizes and energy of orbitals. Azimuthal quantum number. It identifies sub-shell, determines the shape of orbitals, energy of orbitals in multi-electron atoms along with rincipal quantum number and orbital angular momentum, i.

For a given value of n , it can have n values ranging from 0 to n Total number of subshells in a particular shell is equal to the value of n.

Structure of Atom class 11 Notes Chemistry

Magnetic quantum number or Magnetic orbital quantum number m l: Itgives information about the spatial orientation of the orbital with respect tostandard set of co-ordinate axis. Electron spin quantum number ms: It refers to orientation of the spin of theelectron. The region where this probability density function reduces to zero is called nodal surfaces or simply nodes.

Radial nodes: Radial nodes occur when the probability density of wave functionfor the electron is zero on a spherical surface of a particular radius. Angular nodes: Angular nodes occur when the probability density wavefunction for the electron is zero along the directions specified by a particularangle. Degenerate orbitals: Orbitals having the same energy are called degenerateorbitals. Shape of p and d-orbitals. Due to the presence of electrons in theinner shells, the electron in the outer shell will not experience the full positivecharge on the nucleus.

So, due to the screening effect, the net positive charge experienced by theelectron from the nucleus is lowered and is known as effective nuclear charge. Effective nuclear charge experienced by the orbital decreases with increase of azimuthal quantum number l. In the ground state of the atoms, the orbitals are filled inorder of their increasing energies. The order in which the orbitals are filled isas follows: No two electrons in an atom can have the same setof four quantum numbers.

Only two electrons may exist in the same orbitaland these electrons must have opposite spin. Pairing of electrons in the orbitalsbelonging to the same subshell p, d or f does not take place until eachorbital belonging to that subshell has got one electron each i. Arrangement of electrons in different orbitals of an atom.

The electronic configuration of differentatoms can be represented in two ways. Orbital diagram: Symmetrical distribution of electrons- the completely filled or half filled sub-shells have symmetrical distribution of electrons in them and are more stable. Exchange energy-The two or more electrons with the same spin present in the degenerate orbitals of a sub-shell can exchange their position and the energy released due to this exchange is called exchange energy.

The number of exchanges is maximum when the subshell is either half filled or completely filled. As a result the exchange energy is maximum and so is the stability. We are not responsible for any type of mistake in data. All pdf files or link of pdf files are collected from various Resources Or sent by Students.

If any pdf file have any copyright voilation please inform us we shell remove that file from our website. Class 7. Class 8. Class 9. Class Class 6.O2 peroxide formation. These fields aretransmitted in the form of waves. He realized that some of the elements did. Black body: An ideal body, which emits and absorbs all frequencies, is calleda black body.

An isotope of iodine is used in the treatment of goiter.

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