The atomic mass of an element depends upon the mass and relative abundance of each isotope of that element relative abundance of protons in that element mass of each electron in that element mass of each isotope of that element

mass and relative abundance of each isotope of that element

Explanation:-

For example:

If an element X has two isotopes with following masses ad abundance:

Mass of isotope 1 = 267.8 amu

% abundance of isotope 1 = 87.8% = 0.878

Mass of isotope 2 = 269.9 amu

% abundance of isotope 2 = 12.2% = 0.122

Formula used for average atomic mass of an element :

Atoms of the same element do not always have the same mass called Isotopes

Atoms in nature have different masses, so the atomic mass is calculated based on the average mass of all atoms in nature. So that the isotopes of some of these atoms, atomic mass is the average mass of all isotopes in nature

In determining atomic mass, the standard is the mass of 1 carbon-12 atom whose mass is 1 amu (amu = atomic mass unit)

So the obtained atomic mass is the atomic mass relative to the carbon-12 atom

Isotope Cl-35 75.53%, 34.969 amu

Isotope Cl-37 24.47%, 36.966 amu

Average atomic mass Cl = 35.45 amu

So atomic mass of Cl is:

So atomic mass Cl = 35.45

Whereas the Atomic Number (Z) shows the number of protons in an atomic nucleus from an element. If the atom is neutral then the number of protons will equal the number of electrons. So the atomic number can also indicate the number of electrons.

So atomic number = number of protons = number of electrons

Mass Number (A) is the sum of protons and neutrons

Mass Number (A) = Number of protons + Number of Neutrons

So there is a difference between the mass number and atomic mass

The subatomic particle that has the least mass  

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element 2512X  

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Keywords: mass number, atomic mass, amu, isotope  

answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.