what is the mass number of lithium?
148855
Note that mass number is not the same thing as atomic mass; mass number is always a whole number, whereas atomic mass is always an average of the various isotopes of that element.  Lithium can have a mass number of 6, but it's more commonly 7, and its atomic mass is 6.941.
1062179
well, lets think about this\n\navagodro's number is the number of atoms in a mole and =\n6.02 x 10^23\n\nso, if we divide the number of atoms in the problem by the number of atoms in a mole, we will get moles of the atom\n\nI think you get .0027 moles.\na quick glance at the periodic table of the elements will give you the molecular weight for silicon\n28.0855 grams/mole\n\nmultiply and you get .076 or in sci notation, 7.6 x 10^-2\n\nassuming I punched the calculator correctly, it looks like "E".
864891
The isotopic notation is just the mass number (proton + neutron) before the chemical symbol. Since copper has an atomic number of 29 then the isotopic notation respectively, \n63Cu\n\n65Cu
737340
Z = 13    A = 27    The chemical symbol is Al.\nThe sum of the superscripts on the left side of the arrow must equal the sum of the superscripts on the right side of the arrow.  The same is true for the subscripts.  Adding 4 + 26 = 30 for the superscripts on the left, so 27 must be the unknown mass number (A).  Adding 2 + 12 = 14 for the subscripts on the left, 13 must be the missing atomic number on the right (Z).  Z tells you the element, which is aluminum.
814313
First you need to check if your formulas are correct.  Lithium carbonate should be Li2CO3 and chromium (II) carbonate should be CrCO3.  With the correct formulas, the chemical equation is already balanced.
778176
Use the periodic table of the elements.  The "weights" are in grams per mol.  Just use algebra and solve for the number of mols.  Then you know how many atoms there are by the number of mols which is a definite number.
570306
1.ATOMIC NUMBER\n2.ELECTRON\n3.SHELL\n4.ORBIT
593588
atomic mass of S = 32.07, 64 grams of S = 64/32.07 ~= 2 moles\natomic mass of Be = 9.01, 20 grams of Be = 20/9.01 ~= 2.2 moles\natomic mass of Na = 22.99, 25 grams of Na = 25/22.99 ~= 1.1 moles.\n\nThe Na sample has the fewest atoms, followed by K, then S, then Be.
736794
I'll teach you how to do these.  The answer may seem long at first, but just try it, and you'll see it's not as bad as it first appears.  For mass/mass problems, you only have to use the first section of this answer:\n\nToo solve these types of problems, use the following general steps:\n\n[I will use the general word equation: calcium hydroxide reacts with lithium bromide to produce     calcium bromide and lithium hydroxide; as an example, throughout each step, to aid in your learning]\n\n(1)  Write the correct chemical formula for each substance in the reaction.  Be certain each chemical equation is correct!   (ex:  calcium hydroxide:    correct formula  = Ca(OH)2;   NOT CaOH.)\n\n(2)  Write out the chemical equation;   ex:  Ca(OH)2  +     LiBr   gives      CaBr2    +       LiOH    \n\n(3)  Balance this chemical equation;    ex:   Ca(OH)2  +  2LiBr   gives   CaBr2   +   2LiOH\n\n       Note:  this balanced equation is TELLING you that one mole of calcium hydroxide is reacting with 2 moles of lithium bromide to produce (gives) one mole of calcium bromide and 2 moles of lithium hydroxide.  It is TELLING you the relative number of moles of each substance.  \n\n(4)  Determine the MOLE RATIO of the substances involved;  ex:  if the question says you have 1.0 moles of calcium hydroxide and it reacts with an excess of lithium bromide, and asks how many moles of lithium hydroxide are produced,  the answer would be 2.0 moles of lithium hydroxide.  In other words, the MOLE RATIO of calcium hydroxide to lithium hydroxide is 1 to 2, also written as a “1:2 ratio“.    ex:  same question but suppose you have 3 moles calcium hydroxide.  Because the mole ratio  is 1:2, you would produce 6 moles of lithium hydroxide.   A ratio of 3:6  =  a ratio of 1:2;  (you just reduced it to simpler terms).  \n\nStop here if you  are simply given the number of moles of product you have, and asking how many moles of some different substance are produced in a chemical reaction.  \n\n\nSame type of problems, but working with grams instead of moles:\n\nyou simply have to do a couple of extra steps:\n\nI will use the same reaction as above, but will change the question to this:  \n\n“If you have  255 grams of calcium hydroxide, how many grams of lithium hydroxide will be produced, (assuming you have an excess of lithium bromide)”.  \n\n [Note:  unless the question states otherwise, assume you have an excess of the other reactant, thus giving the maximum yield of product; see “Limiting Reagents” below to solve those types of problems]. \n\nTo solve, complete the first 4 steps above (we’ve just done that):\n\n(5)  Convert grams of substance into moles of substance!!!   This is essential in solving these types of problems.  THE KEY STEP FOR ALL PROBLEMS OF THIS TYPE IS TO ALWAYS CONVERT EVERYTHING INTO MOLES FIRST!!!  The general formula’s are as follows:  \n\n                        Moles  =  grams / molecule weight\n\nOr you can use basic algebra and say the following:  \n\n                    Grams  =  Moles   X   molecular weight\n\n[Note:  “molecular weight” is used to describe molecules; “formula weight” is used to describe ionic compounds; and “atomic weight” is used to describe elements;  ALL of them are the sum of all the atomic weights of the elements in the substance. In the case of a single element, alone by itself, this refers to the atomic weight of that element.  Note that the 7 elements:  hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine and iodine only exist as “diatomic” elements, when they are ALONE by themselves (not combined with any other element(s)).  Thus H2, is the correct way to write the chemical formula for hydrogen when it is all alone, by itself.  And it is a molecule, and it’s molecular weight would be equal to 2.0.  This is the same for the all diatomic molecules:  the molecular weight will equal double the atomic weight for that particular diatomic element (because there are TWO a
770649
94,240Pu ---> 40,93Zr + 54,144Xe + _3_ 0,1n\n\nThe first number is the proton number, the second is the nucleon number. Both of these must be conserved in fission. As the number of protons is already conserved, the difference in the nucleon number must come from free neutrons.
703814
211_____207_____4\n      Bi  -->__Tl +____a    (a helium nucleus) \n83_______81_____2
784111
Atomic mass of iron is 55.845 g/mol.  Get a periodic chart. The answer is there.
40725
No, but Krypton is. It's a noble gas. The symbol is Kr, number 36. It has an atomic mass of 83.798(2) g/mol.
150149
Francium has 87 protons.  This information is available on the Periodic Table of Elements, the atomic number (Z) of an element is the number of protons.
900861
As usual, we first check for a balanced equation.  It isn't, so we fix it: 2 LiOH + CO2 -> Li2CO3 + H2O.  Also as usual, get the molecular weights: LiOH = 24, CO2 = 44, and the others don't matter.  There are 4 moles of CO2, so we need 8 moles of LiOH, and that is 192 grams.  Extra credit: find the error in the next response.
663846
It is lithium. Ever heard of lithium batteries? Titanium is a very light metal, but not as light as lithium. It does not occur freely in nature.\n\nIts atomic mass is 6.941 (2) g/mol
95148
Actually, the mass of a proton is 1.00727664669 atomic mass units.\n\nAn atomic mass unit is defined such that Carbon 12 is exactly 12.  The carbon atom weighs less than 12 times the proton (because of nuclear binding energy).