Distinguish between mass number and relative atomic mass of an element - Leaving Cert Chemistry - Question 5 - 2013

The reason the relative atomic mass is rarely a whole number is that it is calculated as the average of the masses of all the isotopes of an element, weighted by their natural abundances. This can lead to fractional values, as isotopes vary in mass.

The Russian scientist was Dmitri Mendeleev.

The elements in the modern periodic table are arranged in order of increasing atomic number (Z), which is the number of protons in an atom's nucleus.

Beta-particle (β-particle): A beta-particle is a high-speed electron ( ext{e}^-) that is emitted during the radioactive decay of an unstable atomic nucleus. It can be negatively charged or positively charged (the latter being called a positron).

A beta-particle is an electron or positron emitted during beta decay. It is characterized by its high speed and ability to ionize surrounding materials.

The half-life of a radioactive isotope is the time required for half of the radioactive atoms in a sample to decay into another element or isotope. After one half-life, 50% of the original substance remains, and this process continues to occur in subsequent half-lives.

One use of carbon-14 is in radiocarbon dating, which is used to determine the age of ancient artifacts and fossils by measuring the amount of carbon-14 remaining in the sample.

To represent the electron arrangement of carbon-14, you can draw the atom with 6 electrons total, where 2 electrons occupy the inner shell and 4 electrons are in the outer shell. This can be represented using dots (•) for each electron:

      •  •  
     • • • •

This indicates that the first shell has 2 electrons and the second shell has 4.