Quantum mechanical model of atom

The Quantum Mechanical Model of the Atom

Energy Is Quantized

After Max Planck determined that energy is released and absorbed by atoms in certain fixed amounts known as quanta, Albert Einstein took his work a step further, determining that radiant energy is also quantized—he called the discrete energy packets photons. Einstein’s theory was that electromagnetic radiation (light, for example) has characteristics of both a wave and a stream of particles.

The Bohr Model of the Atom

In 1913, Niels Bohr used what had recently been discovered about energy to propose his planetary model of the atom. In the Bohr model, the neutrons and protons are contained in a small, dense nucleus, in which the electrons orbit in defined spherical orbits. He referred to these orbits as “shells” or “energy levels” and designated each by an integer: 1, 2, 3, etc. An electron occupying the first energy level was thought to be closer to the nucleus and have lower energy than one that was in a numerically higher energy level. Bohr theorized that energy in the form of photons must be absorbed in order for an electron to move from a lower energy level to a higher one, and is emitted when an electron travels from a higher energy level to a lower one. In the Bohr model, the lowest energy state available for an electron is the ground state, and all higher-energy states are excited states.

Orbitals and Quantum Numbers

In the 1920s, Werner Heisenberg put forth his uncertainty principle, which states that, at any one time, it is impossible to calculate both the momentum and the location of an electron in an atom; it is only possible to calculate the probability of finding an electron within a given space. This meant that electrons, instead of traveling in defined orbits or hard, spherical “shells,” as Bohr proposed, travel in diffuse clouds around the nucleus.

When we say “orbital,” the image below is what we picture in our minds.

To describe the location of electrons, we use quantum numbers. Quantum numbers are basically used to describe certain aspects of the locations of electrons. For example, the quantum numbers n, l, and ml describe the position of the electron with respect to the nucleus, the shape of the orbital, and its unique orientation, while the quantum number ms describes the direction of the electron’s spin within a given orbital.

Below are the four quantum numbers, showing how they are depicted and what aspects of electrons they describe.

Principal quantum number (n)	Has positive values of 1, 2, 3, etc. As n increases, the orbital becomes larger—this means that the electron has a higher energy level and is less tightly bound to the nucleus.
Second quantum number or azimuthal quantum number (l )	Has values from 0 to n – 1. This defines the shape of the orbital, and the value of l is designated by the letters s, p, d, and f, which correspond to values for l of 0, 1, 2, and 3. In other words, if the value of l is 0, it is expressed as s; if l = 1 = p, l = 2 = d, and l = 3 = f.
Magnetic quantum number (ml)	Determines the orientation of the orbital in space relative to the other orbitals in the atom. This quantum number has values from -l through 0 to +l.
Spin quantum number (ms)	Specifies the value for the spin and is either +1/2 or -1/2. No more than two electrons can occupy any one orbital. In order for two electrons to occupy the same orbital, they must have opposite spins.

Orbitals that have the same principal quantum number, n, are part of the same electron shell. For example, orbitals that have n = 2 are said to be in the second shell. When orbitals have the same n and l, they are in the same subshell; so orbitals that have n = 2 and l = 3 are said to be 2f orbitals, in the 2f subshell.

Finally, you should keep in mind that according to the Pauli exclusion principle, no two electrons in an atom can have the same set of four quantum numbers. This means no atomic orbital can contain more than two electrons, and if the orbital does contain two electrons, they must be of opposite spin.

 

Types of chemical bonds

Important Points

• What holds atoms together?
• Review the electron shell model of the atom, valence electrons
• Define chemical bond
• Six types of bonds: ionic, metallic, covalent, polar, hydrogen, and van der Waals. Be able to define each, provide examples, characterize their properties

Atoms in combination: the chemical bond

• So far we discussed the nature of the atom in some detail, and have a qualitative sense of how it looks. However, a lone, non-interacting atom is rare. Most atoms are found in combination with others.
• After the big bang event, the universe began to rapidly expand, and quite soon, within a few minutes, a major component was neutrons. Neutrons are not stable by themselves, so many of them split into protons and electrons, which form a significant component of the universe after about 10-15 minutes. It took about 100,000 years for the temperature of the universe to cool enough for the electrons to attach themselves to the protons and actually form atoms. So, about 100,000 years after the big bang, atoms became a significant component of the universe.
• This tells us that the energies of keeping electrons around a nucleus are much smaller than those associated with the nucleus or the formation of electrons.
• We live in a world of electrons, all our senses, and life itself, is manifest by variations in electronic interactions. Therefore life and humanity can only exist at the lower energy conditions in which electrons are bound to nuclei, i.e. Earth-like conditions and not Sun-like conditions.
• Electrons are the glue that holds groups of atoms together.

Electron shells and chemical bonding

• Let's review the nature of the atom from the point of view of the electrons.
• The atom is mainly low-density space with a very small but dense nucleus that defines the center of the atom.
• Electrons are located around the nucleus.
• These electrons can be classified in terms of shells that correspond to the rows in the periodic table. Each shell can fit a certain number of electrons, depending on how far away from the nucleus it is. A shell that is close to the nucleus can only contain a small number of electrons, otherwise, the electrons are too close together, and electrostatic repulsive forces push them apart. 
• Shells of electrons are most stable when they contain the maximum number of electrons that they can hold. On the one hand, if there are too few electrons, the electrons are constantly whizzing about, trying to fill all available space. Therefore, they have high kinetic energy. On the other hand, if there are too many electrons then electrostatic repulsion takes over and pushes them apart.
• Define the electrons in an unfilled outer shell as valence electrons.
• Since these are the outermost electrons, these are the ones that are perturbed by bringing another atom close by. These are the ones that are involved in bonding.
• Define: a chemical bond is the result of a redistribution of electrons that leads to a more stable configuration between two or more atoms.

Telephone cables

                         Telephone cables.

It was 1984; I was working as junior engineer at telephone exchange Raichur. I was trained in switching [strowger] technology and therefore they put me for indoor job.

The exchange equipment was built on electromagnetic principles. Mechanical switches were used to switch a call as per the calling party dialing signals.

  To maintain the switches in the working order, technicians were employed on routine basis through out the day and night. A senior man known as Mr. Kasikar was the manager of the indoor system. As I was a new fellow, they employed me to update the connection records of working customers. This was needed to settle the billing disputes of customers.

I did prepare such records with the help of office assistants/ operators staff. As a young fellow, I was getting bored as my work was confined to indoor table work. I intended to work in out door as field officer, and I expressed my desire to my boss SDOP Raichur Shri D S Ugarkar. Thus I was posted as JTO Cables and outdoor.

            The struggle:

The external plant constitutes under ground cables and over head open wires part of the telephone system. This was subjected to frequent interruptions due to break downs or contact [loop] faults. Attending to interruptions was the main work involved. Open wire faunlt could be easily located and attended to, by a sectional line man. But when cable fault occurs, it was hell to localize the faulty portion.

            For this, there used to be a team of people like a cable jointer, two labors[mazdoors], and the section lineman and the JTO Cable has to manage the show, and attend to the interruption as quickly as possible in order to keep costumers happy.

 The process [on cable faults]:

1. list out the interrupted telephone numbers, identify the location of the DP[distribution point],_ the end point of cable from where the connections are served, etc.
2. Take out the route map of cable buried in the ground; make a foot inspection to checkup if any new pit dug on the cable route etc.
3. Find out if there is any joint in the cable, nearby. Then ask the cable jointer to dig and localize the faulty cable section.

One Mr. Mohammad Hussein was working as cable jointer. He had a tool kit of jointing materials, an earth meggar to test for low insulation and earth digging apparatus.

            Paper insulated copper wire cables of 0.5 mm diameter were used to construct cable links. If such cable gets punctured the moist mud enters into the bunch of wires and all most all conductors were grounded and potential becomes leaky. No potential reaches to the customer equipment and the phone is dead.

The management problem:

The worker should be well trained, he need be encouraged to take risk, and he should be well paid to keep his workers happy, [the manual labors]. If the fault is localized within a couple of days, and restored by suitable jointing process, the things will be ok. If it takes more time, the things will change to hot discussions and unpleasant tension prevails between the management and the customers.

Network tree of cables:

The exchange is a place, to facilitate inter connection of telephone lines for a moment so that phonic conversation takes place between two parties. That means there should be a permanent physical line of conductors between the exchange and the customer‘s house. And for instantaneous use at any time there should be DC potential of 50 volts between the conductors. This type of working is called central battery system.

            When the system is started with a few lines, say less than 20 lines, they could have been built on open wire lines to start with. As the system grows, the numbers are classified street wise and under-ground pieces of cables are laid into the streets to a suitable centre point. These cables are joined to a main cable and linked to the exchange machine. The electromagnetic switches respond to the customer’s dialing and the connections were established and disconnected automatically.

            If however the line breaks, or short circuit happens, or the wire is grounded, the system does not work and the line is declared as faulty. The customer can not make business through phone.

Field trial:

            Within a week of my joining as JTO Cables, there developed a fault in business locality and dozens of phone lines went out of order. SDOT ordered me to set right the problem. I nodded, but confusion and uneasiness developed in my mind. The previous in charge JTO, was out of station, and I did not have the cable route map nor any experience of handling such situations.

            However we as a team went for foot patrolling and made some enquiries here and there in the middle of the main bazaar. The cable jointer and others associate with cable explained me of the multiple cables running into the street.

            The problem is, there is not a single cable in a street; they lay cables again and again in different periods of time to meet the demand, and therefore to identify a specific cable out of many is again a problem.

            There was one senior operator who had earlier worked as cable jointer and I new him as I was trunk exchange in-charge for some time. We made patrolling and this man gave his experience with the underground matters of Raichur cable network. We had hope now. On a detailed enquiry we came to know that there was a fresh digging at a point in bazaar. We re-dug the place and found the paper insulated cable got punchered and our jointer Mr Mohamed Husain attended to it and I was saved of embarrassment!

The industrial area was far away from the main town. Most of the industrial portion of the town was beyond five kilometers area. And it was very much in need of new connections for business activities. The SDO phones asked me, ‘had the old cable faults be attended it would be easy to provide new lines there.’

A working party was attached for digging and assisting the cable fault localization in industrial area. We use to toil daily till the sun sets, digging and analyzing using the earth meggar and we spent almost one week or so. We reached a place where there was no cable in a section of around ten feet. We joined this missing link to have some new lines to serve new customers.

The JTO Cables job was very challenging in the sense, when there used to be interruption the first man to be responsible was the section officer, the JTO Cables. Costumers used to come with a hope of getting new connection, but when we expressed our inability to service the line due to shortage of lines [pair of cable conductors], they use to say, ‘how is it? A neighbor of my premises is having a connection. why can not you service my line through that?’ and we have to teach him the principles of working of phone lines. He will be disappointed and some times used to accuse, saying “these people are of no use. I think, we have to speak leaders to transfer such idiots”!

They were right, in a sense, the system was primitive and advances had to emerge out of bottle neck. I was one fellow among many officers who were accused for improper planning and delay in doing the network up-gradations in the country. It was 1985-86 year. About 35 -40 years of Indian independence. It was a big challenge to meet the growing demand of phone lines for business.

The parliament was directly involved in formulating the telecom policies and implementations were arranged on piece-meal, due to so many reasons. The huge requirement of material through out the nation was   also a reason.

The advent of microwave started in India around 1985-86. National trunk routes were coming up. The STD was emerging connecting important places, yet the local cabling was not perfected. Here also some changes started happening. Paper core cables were being replaced in phases. If this was implemented, at least service can not go out of order 100% on interrupted cables.

But alas! The man is involved. The crocked ideas of mind are to be eliminated. The most challenging task it was, the staff control. If some one working on the grass- root level, instead of restoring the cable failures starts creating intentionally, only God has to save the situation. But it was a reality, and that was the cruel mind behind actions, that does more damage.

In that sense machines are far better. They are 100% faithful. Infact, the efficiency of government offices was limited to 60 to65 %!  The story need not be elaborated. ‘Power corrupts and absolute power corrupts absolutely’ is the saying. The initial cable construction works were limited. There was only one cable manufacturing factory, in India it seems. Expansions of equipment were very rare. The divisional station Gulberga was a manual switching during 1974-75. It was CB manual switching, in which all activities were manual, including local call connecting by operators.

If someone gets a new connection immediately, it would be a seventh wonder. After 1985, the situation started in better communication drive. The supply chain of materials increased, the execution of cable construction was done through contractors, yet the jointing, and localization of faults was in the hands of a few skilled workers.

The Yermarus camp was about seven kilometers away from the main exchange. A single 20 pair cable was working there, and it went out of order. Such a long distance cable, fault localization was to be done. It went into weeks to do the things to work. A VIP stationed there complained to the General Manager Hubli, about the bad situation of service to Yermarus camp. The general manager came on inspection to witness the actual problem. I was trembling to face him. But he was very polite officer and ascertained the method of fault localization. He inquired about any meters being used to localize the faults. We did not have any meters other than the earth megger. The advent of electronics touched India and solid state fault locators were being manufactured by Aplab Company. He ordered for one such unit to Raichur system.

We received the brand new meter which works on pulse eco reflection method to locate the distance to fault. One fellow, a cable jointer came on deputation to do cable work from Bidar. He was trained in using the meter. We applied his knowledge to locate a fresh fault. The meter worked very fine and just by digging about ten feet distance we could get the damaged portion of cable. This was a turning point in increasing our efficiency of attending the faults. We were saved!

One story goes like this. Operator was eliminated, the trunk efficiency increased, technician was eliminated the switch efficiency increased. Now if the cable jointer be eliminated, the local line efficiency may increase. That may be the reason; all phone mechanics were made cable spillers in due course. At last the creators were eliminated to some degree.

The electronic exchanges era started in India [due to the initiatives of Mr.Sham Pitroda]. The pace of new connections increased. Switches were made available within short period of time with a bulk capacity.

The Raichur office was upgraded to Divisional office. Number of connection went up in stages. The waiting list was long. Suddenly one 300 lines electronic switch was sanctioned and now it was the responsibility of cable section to arrange for increasing cable capacity according to waiting list. Within a couple of weeks the cable plans were prepared and got sanctioned by the competent authority. Now cable lying is to be done on urgency basis to meet the set targets. The divisional office arranged for labor force and immediately the process of digging and lying commenced.  It was a departmental work force on muster roll with senior mazdoors. One S I Phones was given the responsibility of keeping the records of labors and executing the work as required by the cable section.

The digging at main road crossings was done during night hours to avoid the traffic problem. And the cable laying was monitored on daily basis. Thus by the financial year end the new connections were being put into service. And the people were happy to get the phone facility to their residences and business places. The connections crossed 1500 mark.

The Gulbarga city got one E10B switch with all modern facilities. And the earlier imported PRX switch of Gulbarga was diverted to Raichur. This exchange had a capacity of 2000 lines. The most sophisticated computer controlled system is to be installed in the next year immediately. The cable planning was done for suitable up gradation. The existing Strowger switching system which was working on electromagnetic relay system is to be eliminated by installing the modern PRX switch. Here again a technical skill of making parallel wiring of old and new switches was to be implemented to transfer the existing customers to the new system. Cable to cable, pair to pair T- wiring was done with the help of multiple cable jointers. One additional SDE was posted to coordinate the functions. The GM Hubli personally guided the method to be adopted to make T- jointing. This all made me a perfect man of cables.

We transferred the old network to new PRX switch successfully. But the very first day we could not trace out about 200 connections. Again our Divisional Engineer was pointing to me for the inefficient transfer process. I patiently listed the reported numbers and went on ringing one by one. 25% of the problem was solved. All the joints were kept open to stabilize the system. We could not trace about 25 connections of a particular area. We re-examined the T- jointing of that cable and there was a punching problem of some conductors. Again there was a distribution cable fault in gunj locality. All the things got settled in a couple of days.

The system was growing rapidly. One officer was promoted from Gulbarga and was posted to Raichur and he was a cable specialist. He came to lead the Raichur cable system. I was very happy. We shared our knowledge and experience and worked together for next one year. Now our job was to construct, the pillar system. A pillar is a point of isolation on a cable route. All cables going in that direction were terminated on the pillar and loop connections were done to patch the two sides, the exchange side and the distribution side. This facilitates to carry out testing in case of faults and new connections.  The under ground portion was at last modernized and records were updated. The information of spare availability could be assessed accurately.  

                                                                                    

  

 Date of birth: 03-08-1951.

Education    :   B Sc Maths and Physics.

Employment:

            1974- Telephone operator.

            1980- Telephone inspector.

            1084- Junior Engineer.

            1999- Sub Divisional Engineer.

Retired from service on 01-02-2009.

The heart is the center of the universe.

                                     

The heart is the centre of the universe.

Our thoughts and actions that matter; Thoughts are very powerful tools. And thoughts will lead to action. Can we control our thoughts? 

It is you that what makes you happy, not some one else. Respect the absolute freedom of life. Be liberal. Love what you do.  But your act should not come in the way of others freedom. What you expect of others, others also expect the same from you.

Do not keep your eye on someone’s property. Be satisfied with what is available for you. Satisfaction is richness, want is poverty.

            If we practice to live with minimum luggage, we are freer to move. Less luggage more comfort. Keep the bare minimum to be freer. Birds do not carry for tomorrow. They enjoy today and are happy.

            Completely immerse in what you do! Do not blame others; because it is your act. You are only responsible for what you are.

            I am not a citizen of Athens; I am not a citizen of Greece.  I am a citizen of the world. I am a part of the universe.

 They are not my creations, neither your creations, they have come out of the Devine principles. Empty thy mind. Keep it open, the truth enters in it, the beauty that pervades your being.

There is one God, one world and one family. It, the father and all are brothers and sisters. We forget that we are atmas, and we forget that we are brothers and sisters. We indulge in wrong actions like adultery, corruption, hatred and destruction.  We should surrender before the almighty, the Paramatma. What ever I am getting, the good or the bad is surrendered before you, the Supreme power, the God.

            When the desire is completely vanished, the anger also vanishes, and the peace pervades into our personality, the eternal truth opens before us and this state is called the liberation of Atma. Yogi is liberated Atma, and he is always at peace of mind and he is not attached to the actions.

:

           

                       

                                   

           

                       

                                    .

Truthfulness and gentleness must characterize every word. Uprightness and absolute integrity must mask the conduct. 

            Let not one kill any living being; let not one take what is not given him, let not one speak falsely. Let not one drink intoxicating drinks. Let not one be unchaste. Let not one eat untimely food at night. Let not one wear wreaths or use perfumes. Let one lie on a bed spread on the earth.

            Take full responsibility

   Some one else’s opinion of you does not to become your reality.

You cannot control things in life such as nature, the past and other people.

However, you can control your own thoughts and actions.

Taking responsibility for your life is one of the most empowering things you can do.

    Live life on purpose. Write out a plan. Goals that are not in writing are not goals at all; they are merely fantasies. Become an expert. Never give up. Do not delay.

           

            Not by hatred, dear Digavu is hatred appeased. By love dear Digavu hatred is appeased.

            He in whom there is truth, virtue, love, restraint, moderation, he who is free from impurity and is wise, he is called an elder.

            The destruction of life, killing, cutting, binding, stealing, lying, fraud, adultery,  back biting, treachery, cruelty, intoxication, deceit, pride, and bad mind and wicked deeds are what define a man, who can be purified  neither by abstinence from fish or flesh nor by nakedness, tonsure, masked hair, dirt rough garments, penances, hymns, oblations, or sacrifices.