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Wait a minute - where are the neutrons ?We know that opposite charges attract each other, but the converse is also true - the same charges repel each other. When there is just one proton in the nucleus (like the Hydrogen we just looked at), there isn't a problem, but if we had two protons in the nucleus, lying side by side, they would repel each other. They need something to keep them apart. Enter the neutron. If we draw another element, with two protons in the nucleus, we have a different element - Helium. It is the number of protons in an atom that determines which element it is. Because Helium has 2 protons, it needs 2 electrons to be charge neutral
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submitted by cute_ria (36 m) on 25 Sep 2007 12:27:55 IST (3 comments 146 views)
Contact Webmaster Contact Webmaster Atomic Structure An atom is the smallest building block of matter. Atoms are made of neutrons, protons and electrons. The nucleus of an atom is extremely small in comparison to the atom. If an atom was the size of the Houston Astrodome, then its nucleus would be the size of a pea. Scientists use the Periodic Table in order to find out important information about various elements. Invented by Dmitri Mendeleev (1834-1907), the periodic table orders all known elements in accordance to their similarities. When Mendeleev began
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submitted by apurviitjee2008 (1399 m) on 14 Sep 2007 16:41:06 IST (11 comments 243 views)
The Structure of the Atom By the late nineteenth century, most people had accepted Dalton's proposal of 1808 that matter was made of atoms. Dalton "proved" his theory with a number of assumptions, each of which is either factually wrong or was used in a logically inconsistent manner. Nonetheless opposition from critics such as Mach, who never believed in atoms, was largely ignored. Throughout the nineteenth century atomism became an idea that came to dominate thought in a number of fields, including political science, sociology, psychology, biology and more. Then, in 1897 J.J. Thomson discovered the electron. He determined that these electrons
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submitted by johri_anshuman (1183 m) on 16 Nov 2007 10:50:06 IST (21 comments 509 views)
As we increase the number of protons, the number of electrons also increases. As we start to get more and more negative electrons around the nucleus, they will start to repel each other (Electrons have the same charge, and remember that same charges repel). For this reason, the electrons that orbit the nucleus cannot be all bunched together. Like the protons in the nucleus they need to be kept apart. So electrons orbit the nucleus at different distances, forming layers or 'shells' of electrons. This is a little bit like the planets orbiting the sun. In lithium, the 3 electrons are in shells: two in the first, and one in the second shell. The first she
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submitted by cute_ria (36 m) on 25 Sep 2007 12:32:38 IST (1 comments 141 views)
ATOMIC STRUCTURE All things around us are made of atoms. The clothes we wear, the buildings we live in, the air around us, even our own bodies. Atoms are the microscopic building blocks of every solid, liquid or gas. If all the atoms in a substance are the same type - it is called an element. This means it cannot be broken down into any "ingredients". Oxygen (chemical symbol O) is a pure element. Oxygen is oxygen - it is not made up of anything else. If a substance contains more th
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submitted by cute_ria (36 m) on 25 Sep 2007 12:21:50 IST (2 comments 107 views)
SOME POINTS ON QUANTUM NUMBERS... 1) PRINCIPAL QUANTUM NUMBER -> "n" why it is required? To explain the main lines of a spectrum What does it tell..???? a)Main shell in wich an electron resides b)Approx distance of the electron frm the nucleus c)Energy of the shell d)Max no. of electrons present in the shell i.e 2n2 What are the values?? 1,2,3,4,5,6,....i.e any integer Other designations ... K,L,M,N..etc 2)Azimuthal Quantum No. -> "l"... Why is it required?? To explain the fine structure of the line spectrum What does
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submitted by chimanshu_007 (11528 m) on 19 Jul 2007 17:55:01 IST (5 comments 409 views)
John Dalton was an English School Teacher who gave the idea about the existence of atoms. (First look at Fig 1) Dalton relied upon large number of experiments like those mentioned in fig 1 for formulating his hypothesis. The experiments actually strangely indicated the existence of atoms. Dalton said that the atoms were featureless like billiard balls. (look at Fig 2) --------------------------------------------- if there is any mistake please let me know about it. please rate it. if u like it please let me know about it. I am gonna post atomic structure part 2 soon. thanx
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submitted by sinjan.j (574 m) on 11 Aug 2007 20:31:58 IST (1 comments 77 views)
Important Chemical Terms - 2 ATOMIC STRUCTURE · HUND?S RULE: when several orbital of the same type are available, the electrons 1st fill at the orbitals of same energy singly with parallel spins b4 pairing in any orbital takes place. · INFRARED RADIATION: electromagnetic radiations possessing wavelength b/w those of visible light nd those of radio waves, i.e;frm approximately 10-4to 7x10-7 m ·
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submitted by Jyothi (752 m) on 9 May 2007 18:39:20 IST (5 comments 221 views)
1. How many photons of light having a wavelength of 420 nm are necessary to produce 1.2J energy ? 2. Calculate wave number and frequency of radiations having wavelength 5800. 3. Calculate the energy in eV of (i) He+ and (ii) Be 3- in the first excited state. 4. Calculate ratio of de-Broglie wavelength of electron to proton moving with a velocity of 10^5 m/sec. 5. Find out the number of waves made by Bohr electron in one complete revolution in its third orbit. Also calculate the number of revolutions per second that this electron makes around the nucleus? 6. Calculate uncertainty in position of a particle when uncertainty in the momentum is (a) 1 x 10^-2, g
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submitted by sravan (183 m) on 14 May 2007 10:12:50 IST (0 comments 79 views)
1) Important Chemical Terms - 1 Atomic Structure A ALPHA PARTICLE: A sub atomic particle tht has a mass of 4 unit?s nd a charge of +2. i.e.; a doubly charged helium ion (H2+) 2) &nb
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submitted by Jyothi (752 m) on 9 May 2007 18:38:18 IST (6 comments 193 views)
1 1. Canal rays are (a) fast moving electrons (b)slow moving neutrons ( c)deflected by electric field (d)deflected by magnetic field (e) both ( c) & (d) 2. Bombardment of Beryllium by alpha particles by alpha particles led to the discovery of (a)electrons (b)protons ( c)neutrons (d)nucleus (e)positrons 3. The most important defect of Rutherfords model of atom is that (a)it does not mention about the nucleus of atom (b)it does not mention about the equivalence of centrifugal force of revolving electron and the attractive e force of revolving electron ( c)it does not obey the Maxwell law of electrodynamics (d)it does not explain the atomic
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submitted by Jyothi (752 m) on 20 Apr 2007 11:28:20 IST (2 comments 194 views)
1 1. Canal rays are (a) fast moving electrons (b)slow moving neutrons ( c)deflected by electric field (d)deflected by magnetic field (e) both ( c) & (d) 2. Bombardment of Beryllium by alpha particles by alpha particles led to the discovery of (a)electrons (b)protons ( c)neutrons (d)nucleus (e)positrons 3. The most important defect of Rutherfords model of atom is that (a)it does not mention about the nucleus of atom (b)it does not mention about the equivalence of centrifugal force of revolving electron and the attractive e force of revolving electron ( c)it does not obey the Maxwell law of electrodynamics (d)it does not explain the atomic
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submitted by Jyothi (752 m) on 20 Apr 2007 11:28:20 IST (2 comments 194 views)
