# Why is the atomic weight not a whole number?

## Why is the atomic weight not a whole number?

Because the atomic weight is an average based on the percentage of atoms of each isotope in the naturally occurring isotopic mixture (Section 2.6, Example 2.2), atomic weights are not whole numbers even though atomic numbers and mass numbers are whole numbers. Isotopic masses also differ from whole numbers.

Why the atomic mass reported for each element on the periodic table is not a whole number?

The atomic masses of most elements are not whole numbers, because they are a weighted average of the mass numbers of the different isotopes of that element, with respect to their abundances in nature.

### Why is the atomic mass of bromine not 79 or 81?

The atomic mass of bromine (Br) is 79.90. There are two main isotopes at 79 and 81, which average out to the 79.90amu value. The 79 has 44 neutrons and the 81 has 46 neutrons. While it won’t change the average atomic mass, scientists have made bromine isotopes with masses from 68 to 97.

Why are atomic numbers always whole numbers?

Each element on the periodic table has its own atomic number. In fact, this number is how you can distinguish one element from another. The atomic number is simply the number of protons in an atom. Because protons are units of matter, atomic numbers are always whole numbers.

## Why are the atomic masses listed in the periodic table not whole numbers quizlet?

Why are atomic masses of elements not generally whole numbers? The atomic masses listed on the periodic table are a weighted AVERAGE of an element’s isotopes. An element’s atomic number is the number of protons in its nucleus. Number of protons specifies atom type.

Why is the atomic mass on the periodic table a decimal?

The standard atomic weight is the average mass of an element in atomic mass units (“amu”). Though individual atoms always have an integer number of atomic mass units, the atomic mass on the periodic table is stated as a decimal number because it is an average of the various isotopes of an element.

### Why are the atomic weights of the elements generally not integers cite two reasons?

The atomic weights of the elements ordinarily are not integers because: (1) the atomic masses of the atoms normally are not integers (except for 12C), and (2) the atomic weight is taken as the weighted average of the atomic masses of an atom’s naturally occurring isotopes.

Why is the atomic mass of bromine 80?

The mass number = protons + neutrons. Bromine has a mass number of 80 and 35 protons so 80-35 = 45 neutrons.

## How do you find the atomic mass of bromine 81?

where atomic mass = average atomic mass of the element and f.a. = fractional abundance of the isotope. To get f.a., we simply need to divide the given percent abundance by 100. Solving for the mass of Br-81: The mass of bromine-81 is 80.9 amu.

Is atomic mass always a whole number?

Mass number is always an integer. 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.

### Is the atomic number always half the mass?

The mass number of an atom is the total number of protons and neutrons it contains. The mass number of an atom is never smaller than the atomic number.

Why are the atomic masses listed on the periodic table?

Because the atomic mass printed on the Periodic Table is the WEIGHTED average of the individual isotopes.

## How many isotopes of bromine have the same atomic number?

Isotopes are nuclides that have the same atomic number and are therefore the same element, but differ in the number of neutrons. Mass numbers of typical isotopes of Bromine are 79; 81. Atomic mass of Bromine is 79.904 u. The atomic mass is the mass of an atom.

How is the mass and density of bromine determined?

In the periodic table, the elements are listed in order of increasing atomic number Z. Electron configuration of Bromine is [Ar] 3d10 4s2 4p5. Possible oxidation states are +1,3,5/-1. Density of Bromine is 3.12g/cm3. Typical densities of various substances are at atmospheric pressure. Density is defined as the mass per unit volume.

### Why is the atomic mass not a whole number?

Atomic mass is never an integernumber 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.

What is the electron configuration of bromine ( AR )?

Electron configuration of Bromine is [Ar] 3d10 4s2 4p5. Possible oxidation states are +1,3,5/-1. Density of Bromine is 3.12g/cm3. Typical densities of various substances are at atmospheric pressure. Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:

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