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Affiliated programe with wisecleaner√ answered5
876 days ago, last commented by totan1
How do I stop going to facebook5
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I've been searching Firefox add-ons specifically and googling in general5
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new medicine were developed5
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How does your generation differ5
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biologocal weapons by small groups of terrorists?5
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Can love really last a lifetime?5
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chromosomal abberation√ answered5
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parthenogenesis and parthenocarpy√ answeredREWARD $2
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Answers recently replied by totan1

replied the topic Affiliated programe with wisecleaner created by totan1

thanks for helping wisecleaner-admin and umairkhan.

858 days ago
replied the topic Why is baseball called the World Series if it is only played in the US? created by mondy

There were rumors that the NY World newspaper back in the 1800s coined it as thus.

It just morphed into that from the start. I wouldn't worry about it as back in the 1940s even when Wolves beat the touring Moscow Dynamo, the headlines declared that team soccer champions of the world. It's just hyperbole that is based in a pre-Internet past where the world was something that existed mainly on any nation's shores and no one grasped the global nature of sports yet.

The winner of the World Series would be the de facto best club team in baseball in most fans' opinion. Whenever MLB All-Star teams or even club teams tour Japan, they win the series (only lost one series I believe) and these are exhibition series not really taken seriously by MLBers.

876 days ago
replied the topic Why haven't you told them yet? created by zubair

I ll regret of not telling my mom that she is the most beautiful person in my life, that I understand her love and sacrifice for me. I 'll regret of not hugging her, not kissing her on forehead and not telling her that I love her. And why? There's no reason I am just shy to do this.
Every time whe she looks at me in hope and unconditional love, I get this craving to revert back to love her more to tell her that I value her. But then I never have that courage and confidence to confess that she is my weakness, my immense love and to tell her that I exactly know everything about her selfless love. I hope one day I get that spark to do all this at once.

876 days ago
replied the topic What would happen if you buttered the back of a cat and dropped that? created by opera

The paradox arises when one considers what would happen if one attached a piece of buttered toast (butter side up) to the back of a cat, then dropped the cat from a large height. The buttered cat paradox, submitted by artist John Frazee of Kingston, New York, won a 1993 OMNI magazine competition about paradoxes. The idea may not have originated from Frazee since it had appeared on USENET by May 1992, if not before

Some people jokingly maintain that the experiment will produce an anti-gravity effect. They propose that as the cat falls towards the ground, it will slow down and start to rotate, eventually reaching a steady state of hovering a short distance from the ground while rotating at high speed as both the buttered side of the toast and the cat’s feet attempt to land on the ground.[ Kimberly Miner won a Student Academy Award for her film Perpetual Motion.Miner based her film on a paper written by a high-school friend that explored the potential implications of the cat and buttered toast idea.

876 days ago
replied the topic What’s one of your nicknames? What do you prefer to be called? created by moniter

my nicknames are
dadhich sb
I like to be called as ramesh

885 days ago
replied the topic Using only one word per person created by gabber

A positive attitude begins with a healthy self-image. If you will love the way you are and are satisfied, confident, and self-assured, you also make others are around feel the same way.

A negative attitude, on the other hand, has, of course, an opposite effect. So, carrying a negative attitude has a twofold drawback. You feel bad about yourself, and you make others feel the same way.

If you want to have a positive attitude, you have to feature healthy thoughts. This is probably very hard to do nowadays since, all around us, the media feeds us nothing but negative thoughts. A study shows that for every 14 things a parent says to his or her child, only one is positive. This is truly a saddening thought.

If you want a healthier outlook in life, you need to think happy thoughts, and you have to hear positive things as well. So, what can you do? Well, for starters, you could see a funny movie, you could play with children, spend some time telling jokes with friends. All these activities fill you with positive stimuli, which in turn promotes positive attitude.

885 days ago
replied the topic proton or neutron???????? created by malik11

Atomic Theory Revision Notes[edit]
2.1 The Nuclear Atom

2.1.1 : Protons and Neutrons form the nucleus of the atom, electrons orbit the nucleus in electron shells.

2.1.2 : Protons -- Mass = 1 amu , charge = +1 .. Neutrons -- Mass = 1 amu , charge = 0 .. Electron -- Mass = 1/1840 amu (usually insignificant), charge = -1

Simple atom (lithium).png
A simple model of a lithium atom.
Not to scale!
Atoms are made up of a nucleus and electrons that orbit the nucleus.

The nucleus[edit]
The nucleus is made up of positively charged protons, and neutrons, which have no charge but about the same mass as a proton.

Electrons are negatively charged and fly around the nucleus of an atom very quickly. So far, they do not appear to be made up of anything smaller: they are fundamental particles. They are extremely tiny, so small in fact that no one has managed to detect any size whatsoever. They are also very light, much much lighter than either a proton or a neutron. Hence, the weight of the electron is not included in the atomic number.

An atom in its natural, uncharged state has the same number of electrons as protons. If it gains or loses electrons, the atom acquires a charge and is then referred to as an ion. The number of protons in an atom defines its chemical identity (e.g. hydrogen, gold, argon, etc). Protons are not gained or lost through chemical reactions, but only through high energy nuclear processes.

2.1.3 : Mass number (A) -- Number of protons + neutrons. Atomic number (Z) -- number of proton. Isotope -- atoms with same atomic number but different mass number (i.e. different numbers of neutrons)

2.1.4 : AZX... A = mass number, Z = atomic number, X = atomic symbol.

2.1.5 : Isotopes may differ in physical properties (mass/density) and radioactivity but not generally in chemical properties.

2.1.6 : Atomic masses are the average of the atomic mass of each isotope (isotopic mass) times the isotope's relative abundance. results in non integer atomic masses

2.1.7 : Atomic number = number of protons (or number of electrons - ionic charge) , mass number - atomic number = number of neutrons.

2.2 Electron Arrangement

2.2.1 : Continuous spectrum goes continuously through red, orange, yellow, green, blue, indigo, violet. A line spectrum contains only some individual lines from this spectrum.

2.2.2 : Electrons are excited (usually by running an electric current through them). This causes electrons to 'jump' into higher electron shells ( X -> X* ) this state is only temporary, however, and the electron falls back to it's ground state. This change (When the electron falls back from the higher shell to a lower one) decreases the energy of the electron, and this energy is emitted in the form of a photon. If this photon falls into the visible spectrum of light, then it produces a visible spectrum. As electrons move further away from the nucleus, the electron shells become closer together in terms of space and energy, and so lines converge towards the end of the spectrum.

Wave nature of electrons[edit]
Electrons behave as particles but also as waves.

One of the results of this observation is that electrons can not orbit with any energy they like. Think of a standing wave on a guitar string. Only a whole number of half wavelengths will fit in the string to form a standing wave, likewise for an atomic shell. Since the energy is dependent on the wavelength this means that the energy of an electron in an atom (a bound electron) is quantized. This means that the energy is limited to certain distinct values, one for each shell with no middle values allowed.

2.2.3 : The main electron levels go : 2, 8, 18 etc...2n + 2 for n0, n1 and n2...

2.2.4 : Electrons are added from the left...after each shell is filled, move to the next...2, 8, 18...only up to Z = 20 is required.

HL Material[edit]
Topic 12 is the additional HL material for Topic 2.

It's not just the energy that is quantized, other properties that an electron can posess are also split into distinct units with no in betweens. The angular momentum is quantised, the spin is quantised, the component of the angular moment in any direction that you care to choose is quantised. There are in fact a whole host of rules determining the values that each of these properties can take.

Electron shells[edit]
Each different shell is subdivided into one or more orbitals, each of which has a different angular momentum. Each shell in an orbital has a characteristic shape, and are named by a letter. They are: s, p, d, and f.

In a one electron atom (e.g H, He+, Li++ etc.) the energy of each of the orbitals within a particular shell are all identical. However when there is more than one electron, they interact with one another and split the orbitals into slightly different energies. Within any particular shell, the energy of the orbitals depends on the angular momentum, with the s orbital having the lowest energy, then p, then d, etc.

The s Orbital[edit]
The simplest orbital in the atom is the 1s orbital. The 1s orbital is simply a sphere of electron density.

There is only one s orbital per shell. The s orbital can hold two electrons, as long as they have different spin quantum numbers.

The p Orbitals[edit]

Stylised image of all the 2p atomic orbitals.
Starting from the 2nd shell, there is a set of p orbitals. The angular momentum quantum number of the electrons confined to p orbitals is 1, so each orbital has one angular node. There are 3 choices for the magnetic quantum number, which indicates 3 differently orientated p orbitals. Finally, each orbital can accommodate two electrons (with opposite spins), giving the p orbitals a total capacity of 6 electrons.

The p orbitals all have two lobes of electron density pointing along each of the axes. Each one is symmetrical along its axis. The notation for the p orbitals indicate which axis it points down, i.e. px points along the x axis, py on the y axis and pz up and down the z axis. The p orbitals are degenerate, they all have the same energy. P orbitals are very often involved in bonding.

2px 2py 2pz

The d Orbitals[edit]
The first set of d orbitals is the 3d set. There are 5 choices for the magnetic quantum number, which gives rise to 5 different d orbitals. Each orbital can hold two electrons (with opposite spins), giving the d orbitals a total capacity of 10 electrons.

Note that you are only required to know the shapes of s and p orbitals for the IB.

In most cases, the d orbitals are degenerate, but sometimes, they can split, with the eg and t2g subsets having different energy. Crystal Field Theory predicts and accounts for this. D orbitals are sometimes involved in bonding, especially in inorganic chemistry.

Material for new syllabus[edit]
SL TOPIC 2.1 THE ATOM (1H).[edit]
SEE NEUSS, P6-7 TOK: What is the significance of the model of the atom in the different areas of knowledge? Are the models and theories that scientists create accurate descriptions of the natural world, or are they primarily useful interpretations for prediction, explanation and control of the natural world?

The position of protons, neutrons and electrons in the atom.[edit]
Here is a typical atom, helium:


TOK: None of these particles can be (or will be) directly observed. Which ways of knowing do we use to interpret indirect evidence gained through the use of technology? Do we believe or know of their existence?

909 days ago
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