How many atoms of hydrogen are needed to create an atom of helium?
822799
First three answers are not correct.  The answer, for normal hydrogen and helium, is four.  Two of the protons will convert to neutrons, with the emission of positrons and neutrinos.  The positrons will annihilate with two of the original hydrogen electrons, each throwing a pair of 511 kev gamma rays.  The remaining two electrons will tie up with the helium.  This is the reaction that powers the sun.
742814
They are isotopes. Different isotopes of the same element can exist and these are caused by differing number of neutrons.\n\nThe "common" isotope of Helium is Helium-4 (it has 2 protons and 2 neutrons, hence the 4). \n\nHelium-3 is a variety of Helium (far less common than Helium-4) which has two protons but only one neutron.
726228
It is hydrogen (H). Hydrogen must always exist as a compound, forming a covalent bond with another hydrogen atom (H2).\n\nAtoms such as this are called 'diatomic'. There are others (N, O, F, Cl, Br, and I), however, only H is the stuff of the sun.\n\nUse the extra info to dazzle your teacher.\n\n. . .  and if you didn't know, now you do . . .
661461
helium,.........,hydrogen,............, and oxygen??? I don't have the book on me right now, so I am drawing a blnk
712651
Mostly hydrogen, some helium, and relatively small amounts of various other elements.
889364
i am just starting chemistry, but i think that you multiplied hydrogen (H) by four, when it should be multiplied by 3, like the Oxygen (O).  otherwise it is correct.  you sould round to whatever your teacher tells you or to 6 significant digits, because that is the least amount you have.  the correct answer should be \n\n(considering your atomic weights are correct)\n\n[12.0107 x 3] + [1.00794 x 5] + [15.9994 x 3] + [1.00794 x 3] =  \n\ncalculate it out and it should work fine... (i think)
744373
For the first one, multiple the number of moles by the molecular mass of Helium.  Helium is mono-atomic (one atom per molecule) so the atomic mass of Helium is used:\n\n4.56 moles * 4.003 g/mol = ? (you can at least do the math)\n\nFor the second part, each mole of pure substance contains Avogadro's number of molecules (or atoms for an element).\n\nThe number of moles of Zinc is the mass divided by the atomic mass (also called the atomic weight).  For Zinc this is 65.38 g/mol:\n\n12 g / 65.38 g/mol = number of moles of Zinc.\n\nEach mole contains 6.022 * 10^23 atoms of Zinc, so just multiple the number of mole above by 6.022 * 10^23 atoms/mole to get your answer.
864550
The number of particles in a mole of anything is 6.02 x 10^23 (Avogadro's Number). So, since neon is a noble gas, in its natural state it will bond with itself in pairs of 2, meaning that a mole of neon molecules would have (6.02x10^23)x2 atoms.
530899
Helium has two electrons, so it's first shell is full.
354063
yes, it's the 1s orbital. The electron configuration of hydrogen is 1s1.  The electron configuration of helium is 1s2.
1031597
That 1kg of hydrogen would convert to about 0.954 kg of helium, the other 0.046 kg is changed to energy.\n\nE=MC^2\nM=0.046 kg\nC=300,000,000 m/s\nE=4.14X10^15 joules\n  = 1,150,000,000 Kilowatt-hours
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.
833318
Hydrogen.  To be more specific, the H1 isotope.  The deuterium or H2 atom is only one in eight thousand of all hydrogen atoms.\nThe second most common element, helium, is less than 10%.  All others together are a minor component, no matter how important to us.
292346
26 electrons. If it's an electrically neutral atom, then the number of protons must equal the number of electrons.
693223
Yes an atom is the same as an element.  A single atom is the smallest particle of an element.  There are 118 different elements in the periodic table. For example, a Hydrogen atom is one proton and one electron.  The next element in the periodic table is Helium, it has one proton, one neutron and one electron.  Each of these atom examples represent their own element.  So you see a single atom does represent it's own particular element, as discussed in the Hydrogen and Helium examples.
180938
ex: 2 hydrogen atoms and 1 oxygen atom combine to create 1 molecule of H20(a chemical change).
176876
The gas in the balloon is helium. These helium atoms were once the alpha particles of radioactive decay trapped with other particles beneath the ground in natural gas deposits. For each uranium atom that decays to lead, 8 alpha particles are emitted. An alpha particle with 2 electrons is a helium atom.