how can we say that an orbital contains only  two electrons?
928403
You must be one of those people who only believe in things they can tactilely handle.  The world of incredibly small objects will be a philosophical challenge, but I'm sure you're up to it.   \n\nFirst, let me give you the short and easy answer:  \n\nThe entire universe runs on a few very simple mathematical equations.  The solution of these equations is extremely difficult, but they perfectly predict and describe physical reality (when solved perfectly), so we're pretty happy with them.  \n\nMathematically speaking, orbitals and electrons exist, and because they exist and have certain properties, they must obey certain rules.  One of those rules is that only two electrons can ever fit into the same orbital, and they have to have opposite spin.  Any random orbital may have zero, one or two electrons but no more because if you tried to shove a third (or more) electron into an orbital, the orbital would vanish.  Think of it this way... its the only way that the elctrons can forever coexist without ever crashing into each other or falling apart in a chaotic state, because electrons (by Coulomb's law) HATE each other and strive to maintain maximum distance from one another while all trying to get close to the positively charged nucleus, which they LOVE.\n\nNow for the long answer:\n\nBefore you can accept that two electrons go into an orbital, you need to be able to accept that electrons exist.  JJ Thompson is credited with discovery (though not postulation of) the electron in his famous cathode ray experiments.  Electrons are evidenced regularly on a macroscopic scale through the use of electricity (the name is not coincidental!) and in such interesting objects as scanning tunneling microscopes and electron microscopes.  Robert Miliikan managed in 1901 to measure the charge on the electron in his oil-drop experiments.\n\nAn important piece of information came through Ernest Rutherford's (and his students Hans Geiger and Ernest Marsden) experiments on gold foil wherein they demonstrated that the mass of an atom resided in a small region of space in its center, which had a positive charge.  Later, Niels Bohr proposed that electrons reside in orbits around the nucleus, which would contain the protons and neutrons (both already demonstrated to exist independently).  The usefulness of Bohr's model was widely realized because it could predict experimentally observed phenomena, such as why atomic emission spectra have discrete lines while blackbody radiators give broad spectra.  \n\nA key moment in Bohr's theory was the existence of discrete energy states (that is, well-separated) that electrons could exist in.  The electrons could change energy levels, but could not occupy any energy states between those energy levels. The idea was hardly unique to Borh, having originated with Max Planck and Albert Einstein in reference to photons; yet its application to the atom was Bohr's own contribution.\n\nThis theory was pretty good, but it was a little rough.  Many very good physicists decided to work on the combination, including Paul Dirac and Erwin Schrödinger.  The final equation describing the behavior of quantum systems (and in particular atomic structure and the resultant properties) is known as the Schrödinger equation.  Solution of the Schrödinger equation provides perfect agreement with experiment (i.e. Balmer series of hydrogen) where the solution is exactly possible, and within experimental error where it is not. The Schrödinger equation is a simple, elegant, yet frighteningly hard mathematical equation relating the energy of a system to its wavefunction descriptor (remember, Einstein already showed wave-particle duality):\n<Ψ | H | Ψ > = E\n\nMax Born showed that if you multiply the wavefunction ( Ψ) from the Schrödinger equation by itself (i.e. Ψ*Ψ ) you will get a shape that corresponds to the region of space in which electrons that can exist in that level of energy (wavefunction) mo
712831
The Relationship of Electrons and Valence\n\nFor purposes of describing chemical behavior, an atom can be considered as a positively charged nucleus surrounded by negatively charged electrons orbiting in concentric spherical shells. The number of positive charges in the nucleus determines how many electrons normally surround the nucleus; as atomic number increases, the electron shells are filled, starting with those nearest the nucleus.\n\nThe valence of an atom is determined by the number of electrons in the outermost, or valence, shell. The atom exists in its most stable configuration when its outermost shell is completely filled; in combining with other atoms, it thus tends to gain or lose valence electrons in order to attain a stable configuration. If the valence shell of the atom is nearly complete, as in chlorine and other nonmetals, the atom will tend to accept electrons to complete it; if the valence shell has few electrons, as in potassium and other metals, the atom will tend to lose these electrons, so that the next shell below the valence shell becomes a completed outermost shell.\n\nThe valence of many elements is determined from their ability to combine with hydrogen or to replace it in compounds. For example, one oxygen atom combines with two hydrogen atoms to form water and the valence of oxygen is thus determined to be 2. Similarly, chlorine accepts one electron in combining with a single atom of hydrogen to form hydrogen chloride, HCl, and chlorine's valence is 1. Zinc does not combine with hydrogen but does replace it in compounds; in a typical replacement reaction, one zinc atom replaces two hydrogen atoms, as in the equation Zn+H2SO4→ZnSO4+H2, so that zinc has a valence of 2.
850997
sp : 2 orbitals (1 from s & other from p; rearranging to give 2 orbitals of equivalent energey & value)\n\nsp2: 3 orbitals\n\nsp3: 4 orbitals\n\nsp3d: 5 orbitals\n\nsp3d2:  6 orbitals\n\n\nany further clarifications \n\nhttp://en.wikipedia.org/wiki/Orbital_hybridisation
895042
All 's' can hold 2 electrons.\n\nAll 'p' can hold 8 electrons.\n\nAll 'd' can hold 18 electrons.\n\nAll 'f' can hold 32 electons.
844206
The answer is simple. All elements (whose basic units are atoms) except the noble gases, have less than 8 electrons in their valence shells.  The rule that states that atoms should have 8 electrons to achieve stability is called The Octet Rule.\n\nhttp://en.wikipedia.org/wiki/Octet_rule\n\nThe way that they can attain 8 electrons is by forming BONDS: by either sharing electrons (covalent bond) or by gaining/losing electrons (ionic bond).   This is the main reason why atoms react: to attain 8 valence electrons.\n\nIf we look at it at another angle, we can say that atoms react in order to decrease energy.  This comes from the principle that bond formation results in loss of energy, and that stability comes from decreased energy.\n\nHope that helps.
283736
The octet rule refers to Lewis dot diagrams and how electrons are arranged in molecules. During covalent bonding, atoms have eight electrons in their orbit, whether or not they are shared with another atom. An example of the octet rule would be oxygen atoms (each with 6 electrons) in a diatomic oxygen molecule sharing a total of four electrons between each other while keeping four electrons to themselves. Of course, the octet rule does not apply to hydrogen, which can only hold two electrons. The octet rule also applies to ionic bonding, where the anion (the negatively charged ion) gains a number of electrons to  have a total of eight electrons in its orbit.
422168
No it's false. It's an Ionic bond (e.g.: Na+Cl-)\n\nA Covalent bond is where two atoms opt to share electrons (to complete their valence shell) e.g.: atomic Oxygen has 6 valence shell electrons (L shell or 2s2,2p4) by sharing two of it's electrons with two from another Oxygen atom means that the four electrons shared form 2 covalent bonds and give the impression (if you will) that each oxygen has 8 valent electrons (a complete L shell)
145018
It does not just have to do with Bohr's quantum number (n). It is also to do with the angular momentum quantum number(L) and electron spin (+1/2 or -1/2). Therefore, if n=1, L can only = 0 and the result is 2 electons. One with a spin of +1/2 and the other with a spin of -1/2. \nIf n=3, L can be either 0,1, or 2. \nMeaning, \nif n=3 and L=0 this results in 2 electrons on the sub-shell. \nIf n=3 and L=1 this results in 6 electrons on the sub-shell. \nIf n=3 and L=2 this results in 10 electrons on the sub-shell.\n\nThis results in a maximum of 10+6+2 = 18 electrons in the shell.\n\nThis is because if L=2, the maximum number of possible electron states on a sub-shell of n=3 are as follows:\n\nGiven, m = -L, -(L-1)..0..(L-1), L\n\nm(magnetic quantum number) can have a value of -2, -1, 0, 1, 2 with the electrons having a spin of +1/2 or -1/2 resulting in a maximum of 10 electons in that sub-shell.\n\nThis is all based on the Pauli Exclusion Principle which states no two fermions (electrons) can exist on the same sub-shell with the same spin and magnetic quantum number(m).
570306
1.ATOMIC NUMBER\n2.ELECTRON\n3.SHELL\n4.ORBIT
191934
Two in the first shell. 10 in the second shell. 10 in the third shell. 5 in the 4th shell for neutral Manganese. Mn 2+ is missing 2 electrons, so it would only have 3 in the outer shell. The rest will stay the same.\n\nHere's a cool interactive periodic table that may help you with your homework. \n\nhttp://www.webelements.com/\n\nYou can click on the the element you are interested in, then in the column on the left you can go to electronic properties and it will show you how the electrons are distributed. You can add or remove electrons to configure the electron arrangement of various ions of the substance you are interested in.
948808
Electron is simply the smallest and ligthest subatomic particle inside every atoms. as you know, atom consists of protons (positively charged), neutrons (no charge) and electrons (negatively charged). you can imagine atoms to be like a planet which has meteors orbiting around it. the planet represent the nucleus which consists of the protons and the neutrons. and the meteors around are representing the electrons. due to its light weight, electrons move around in an incredible speed around the nucleus. however, electrons do not escaped from the nucleus because they are bounded by forces which keep them in tracks. you can check it out in www.wikipedia.com if you need more info on electrons :D . GL for ur science fair anw.
261927
Actually I think there would be three dots:\n                    .B: \nRemember that Boron has three electrons in the second energy level and five total.\n\nThe sites below should have some good answers for your future Chemistry related questions.\n\nGood luck on your homework,\nArmus
965017
You need to know the number of valence electrons.  Carbon, for example, would want to pair with 4 other atoms.  If there were fewer atoms attached as in CH2O (only 3 attached to the carbon) then one of the atoms must be double bonded.  In this case it is the oxygen that would have the double bond.  You could deduce the approximate shape from the number of bonds.  It would be slightly distorted by the slight negative polarity of the oxygen atom.  Shape of a molecule is a complicated issue that I glossed over.
669373
Electron Dot Formula, aka Lewis Dot Formula, comprises with the octet rule, which states that any stable compound (or element) must have eight electrons in its outer shell. But sometimes, Lewis Dot Formula is just a representation of any molecule just to give perspective on the pairing or sharing of electrons during a reaction.\n\nfor example:\n\nHydrogen gas has only 1 electron to fill up its orbital shell, Oxygen has 6 electrons on its outer shell, that's why this diatomic element needs 2 electons to become stable. Using Lewis Dot Formula:\n\n(note: i use + to indicate dot)\n\nH+ +O+ +H -------->  H:O:H \n(this H:O:H is the Lewis Dot Formula for water)
761557
Any atom in main group chemistry can only have a maximum of 8 electrons in its valence orbital (outter shell).\n\nelements want to have this magic number of 8 electrons in there outter shell.  For example the formation of NaCL.  Sodium (Na) has 1 electron in its outter oribital, chlorine (CL) has 7 electrons in its outter shell.  Therefore Na and CL want to form an ionic compund so they both have 8 electrons in there outter shell.\n\nCovalent compounds work in a similar way, except There will be transfer of electrons rather than electron sharing.\n\nThe reason its 8 is because of the S and P orbitals.  there can be a maximum of 2 in the S orbital and 6 in the P orbital.  \n\nThis is an over simplification though as there are orbitals which can hold more than 8 electronsd and f orbitals in the transition metals), but its the basic idea you are taught at your level of chemistry ^^
969429
92 protons and 92 electrons\nIsotopes have a different number of electrons
1128901
An electron/energy shell, is a group of atomic orbitals with the same value of the principal quantum number n. \nThus in a silicon atom (1s^2  2s^2 2p^6 3s^2 3p^2)  the number of energy shells with electrons in them is 3.\n\n(just for info: There are 5 occupied subshells (1s, 2s, 2p, 3s, 3p) and 8 occupied orbitals 1s 2s 2px 2py 2pz 3s 3px 3py, out of which the first 6 have 2 electrons and 3px and 3py have one electron each; Hund's rule doesn't allow an electron pair in 3px while the other 3p orbitals are empty)