Sage-Tips

Why does chlorine have an atomic mass of 35.5 which is not a whole number?

For example, the relative atomic mass of chlorine is 35.5 rather than a whole number. This is because chlorine contains two different isotopes, chlorine-35 and chlorine-37. The table shows the mass numbers and abundances of the isotopes of copper in a naturally-occurring sample.

Has an average atomic mass of 35.5 amu?

Chlorine
Chlorine has an atomic weight of 35.5 AMU.

Why should the relative atomic mass of chlorine be closer to 35 than 37?

Notice that the answer is closer to 35 than it is to 37. This is because the chlorine-35 isotope is much more abundant than the chlorine-37 isotope. The table shows the mass numbers and abundances of naturally-occurring copper isotopes.

What is the relative mass of an atom?

The relative atomic mass of an element is defined as the weight in grams of the number of atoms of the element contained in 12.00 g of carbon-12. 75.53 of these atoms each have a mass of 35 atomic mass units (AMU), and 24.47 atoms each have a mass of 37 AMU.

Why is chlorine atomic mass fractional?

It has atomic number 17, chlorine have fractional atomic mass number because it has two isotopes having atomic mass number 35 and 37 in the ratio 3:1. This is because the atomic weight used in the periodic table and calculations is the average mass of its isotopes whose atomic masses are 34 and 35.

Why relative atomic mass is not a whole number?

Relative isotopic masses are always close to whole-number values, but never (except in the case of carbon-12) exactly a whole number, for two reasons: protons and neutrons have different masses, and different nuclides have different ratios of protons and neutrons.

Why is the relative atomic mass not always a whole number?

The relative atomic mass of an element has a value between the mass numbers of the lightest and heaviest isotopes of the element. Its value is always closer to the most abundant (most common) isotope. The relative atomic mass is often not a whole number since it is an average mass of one atom of the element.

Why is atomic mass of chlorine taken as 35.5 μ and not a whole number like 35 μ or 36 μ explain?

Answer: The reason for the atomic mass of chlorine taken as 35.5u and not as 35u because of the presence of isotopes. Isotopes are defined as variants of a particular element where these variants will have the same number of protons but differ in the number of neutrons in the atom.

Why is relative atomic mass not a whole number?

Atomic mass is never an integer number for several reasons: The atomic mass reported on a periodic table is the weighted average of all the naturally occuring isotopes. Being an average it would be most unlikely to be a whole number. The mass of an individual atom in atomic mass units is the mass relative to carbon-12.

Why is the atomic mass fractional?

Reason for fractional atomic mass: The atomic masses of most elements are fractional because they exist as a mixture of isotopes of different masses. Since the atomic mass of isotopes are different, so average atomic mass is calculated for a single element.

How do you find the relative atomic mass of chlorine?

In other words, in every 100 chlorine atoms, 75 atoms have a mass number of 35, and 25 atoms have a mass number of 37. To calculate the relative atomic mass, Ar, of chlorine: [textit {A}_textup {r}=frac {total~mass~of~atoms} {total~number~of~atoms}=frac { (35times75)+ (37times25)} { (75+25)}]

What is the relative atomic mass of an element?

The relative atomic mass of an element is a weighted average of the masses of the atoms of the isotopes – because if there is much more of one isotope then that will influence the average mass much more than the less abundant isotope will. For example, chlorine has two isotopes: 35Cl and 37Cl. But the relative atomic mass of chlorine is not 36.

Why is the mass of a C atom 12 amu?

We do not simply state the themass of a C atom is 12 amu because elements exist as a variety ofisotopes. Carbon exists as two major isotopes, 12C, and 13C (14C exists and has a half life of 5730 y, 10C and 11C also exist; their half lives are 19.45 min and 20.3 days respectively).

Why are the masses of elements determined relative to 12C?

All the masses of the elements are determined relative to12C. By the way, the mass of an element is not equal tothe sum of the masses of the subatomic particles of which the elementis made! AverageAtomic Mass Since many elements have a number of isotopes, and since chemistsrarely work with one atom at a time, chemists use average atomicmass.