Cecille's Creativity

I love Chemistry and I love my professor everytime she teaches us this subject. Before, it doesn't give me much interest learning the lesson but as time goes by, I have learned that Chemistry is an interesting subject. That is why, I will share to you on the things that makes me love most of Chemistry.

Atomic Number
Atoms are composed of identical protons, neutrons and electrons. How then are atoms of one element different from another element? Element are different because they contain different numbers of protons. The "atomic number" of an electron is the number of protons in the nucleus. The number of protons in an atom is equal to the number of electrons. Atomic Number (Z) of an element is the number of protons in the nucleus of each atom of the element.

Mass Number  is the number of protons and neutrons in the nucleus of an isotope.
Complete Symbol of the element, the mass number and the atomic number.

Isotopes
Dalton was wrong about all elements of the same type being identical. Atoms of the same element can have different numbers of neutrons. Thus, different mass numbers. These are called isotopes.

Frederick Soddy (187719) proposed the idea of isotopes in 1912. Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons. Soddy won the Nobel Prize in Chemistry in 1921 for his work with isotopes and radioactive materials.

Measuring Atomic Mass
Instead of grams, the unit we use is the Atomic Mass Unit (amu). It is defined as 1/12 the mass of carbon 12 atom. Each isotope has its own atomic mass, thus we determine the average from percent abundance.

To Calculate the Average Mass
Multiply the atomic mass of each isotope by its percent abundance, then add the results. If not told otherwise,  the mass of the isotope is expressed in atomic mass units (amu).