2006-07-15 06:01:43 · 17 answers · asked by Segun 2 in Science & Mathematics ➔ Chemistry
Its C12.
In the old days it was H and then shifted to O (16) and now the standard is C(12) atom
AMU = Weight of one mole of the atom / weight of one mole of C(12)
2006-07-15 06:06:46 · answer #1 · answered by Tharaka D 2 · 2⤊ 1⤋
atomic mass
the mass of a single atom, usually expressed in atomic mass units (amu). Most of the mass of an atom is concentrated in the protons and neutrons contained in the nucleus. Each proton or neutron weighs about 1 amu, and thus the atomic mass is always very close to the mass number (total number of protons and neutrons in the nucleus). Atoms of an isotope of an element all have the same atomic mass. Atomic masses are usually determined by mass spectrography (see mass spectrograph). They have been determined with great relative accuracy, but their absolute value is less certain.
At one time, the lightest atom was assigned a mass of 1 amu and the mass of any other atom was expressed in terms of this standard. Today atomic mass units are defined in terms of the 12C isotope, which is assigned a mass of exactly 12.000... amu.
2006-07-15 06:13:35 · answer #2 · answered by Anonymous · 0⤊ 0⤋
the atomic mass unit was defined by molar ratios of the Carbon-12 isotope
2006-07-15 13:54:07 · answer #3 · answered by Mama R 5 · 0⤊ 0⤋
One twelfth of a mass of an atom of the carbon-12 isotope; a unit used for stating atomic and formula weights; also called dalton.
-Does that help? I just did a search
2006-07-15 06:05:52 · answer #4 · answered by amazonbia 3 · 0⤊ 0⤋
The isotope Carbon 12 was used to define the amu. 1/12th of C12 equals 1 amu and the rest of the elements are based on that.
2006-07-15 09:10:47 · answer #5 · answered by Anonymous · 0⤊ 0⤋
CARBON-12 WAS THE ISOTOPE USED TO DEFINE THE MASS OF THE ATOMIC MASS UNIT.FIRSTLY OXYGEN WAS USED BUT THAN IT WAS NOT GIVING THE REQUIRED RESULTS .ONE AMU IS DEFINED AS 1/12 MASS OF C-12
2006-07-15 06:08:19 · answer #6 · answered by juhi 3 · 0⤊ 0⤋
The unified atomic mass unit (u), or dalton (Da), is a small unit of mass used to express atomic and molecular masses. It is defined to be 1/12 of the mass of one atom of carbon-12.
2006-07-15 06:06:38 · answer #7 · answered by eric l 6 · 0⤊ 0⤋
Carbon has an atomic mass of exactly 12 so the atomic mass unit is 1/12 of that of carbon. It used to be that hydrogen was exactly one however it is now about 1.008.
2006-07-15 06:14:29 · answer #8 · answered by Tom D 2 · 0⤊ 0⤋
Carbon-12 1/12th the mass of a Carbon-12 equals 1 amu
2006-07-15 06:05:09 · answer #9 · answered by piercesk1 4 · 0⤊ 0⤋
H and O can be used too its just that its simpler using Carbon12. If you were to use Oxygen or Hydrogen as the atomic mass unit the ratio would come out to be the same
2016-03-27 06:28:54 · answer #10 · answered by Anonymous · 0⤊ 0⤋
Carbon 12. Due to its abundance in nature, a twelvth of a carbon atom was used as a atomic mass unit(amu) which still stands to this day.
2006-07-15 11:13:25 · answer #11 · answered by haroun i 2 · 0⤊ 0⤋