Isotopes & Ions 4.7; 4.10

Subatomic Particles

Remember Dalton?  Remember Dalton’s atomic theory?  “All atoms of a given element are identical”.  WRONG!  All atoms of the same element contain the same number of protons and electrons, but atoms of a given element may have different numbers of neutrons.  Remember Dalton’s atomic theory?  “All atoms of a given element are identical”.  WRONG!  All atoms of the same element contain the same number of protons and electrons, but atoms of a given element may have different numbers of neutrons.

Isotopes  All atoms of an element have the same number of protons  The number of protons in an atom of a given element is the same as the atomic number  found on the Periodic Table  Atoms of an element with different numbers of neutrons are called isotopes  All isotopes of an element are chemically identical  undergo the exact same chemical reactions  Isotopes of an element have different masses  Isotopes are identified by their mass numbers  mass number = protons + neutrons  All atoms of an element have the same number of protons  The number of protons in an atom of a given element is the same as the atomic number  found on the Periodic Table  Atoms of an element with different numbers of neutrons are called isotopes  All isotopes of an element are chemically identical  undergo the exact same chemical reactions  Isotopes of an element have different masses  Isotopes are identified by their mass numbers  mass number = protons + neutrons

Isotope Notation

Examples 1.Determine the number of each of the three types of subatomic particles for each of the following: Co Cl U 2.Write the symbol for each of the following atoms 1.A cesium atom with 77 neutrons 2.An iron atom with a mass number of 56 1.Determine the number of each of the three types of subatomic particles for each of the following: Co Cl U 2.Write the symbol for each of the following atoms 1.A cesium atom with 77 neutrons 2.An iron atom with a mass number of 56

Average Atomic Mass  Carbon has a mass listed of a.m.u., but no isotope of carbon has a mass of  How is this the mass reported for carbon?  Atomic masses are the weighted average of the masses of the isotopes.  Carbon has a mass listed of a.m.u., but no isotope of carbon has a mass of  How is this the mass reported for carbon?  Atomic masses are the weighted average of the masses of the isotopes.

Sample Problem  Carbon has 13 naturally occurring isotopes, however, only two isotopes are stable, carbon-12 and carbon % of all carbon is carbon-12 while 1.03% is carbon-13. All other isotopes are insignificant in abundance. What is the average atomic mass of carbon?

Try another one 1.Element Xa (imaginary) occurs in three forms, Xa-82 (82.0 amu), Xa-83 (83.0 amu), and Xa-85 (85.0 amu). The relative abundances of the atomic masses are 0.35%, 3.65%, and 96.0% respectively. Calculate the average atomic mass of the imaginary element, Xa.

IONS  A charged entity is called an ion.  IMPORTANT: PROTONS STAY IN THE NUCLEUS; IONS ARE FORMED THROUGH THE GAIN OR LOSS OF ELECTRONS!!!  A positive ion is called a cation formed when an atom loses electrons  A charged entity is called an ion.  IMPORTANT: PROTONS STAY IN THE NUCLEUS; IONS ARE FORMED THROUGH THE GAIN OR LOSS OF ELECTRONS!!!  A positive ion is called a cation formed when an atom loses electrons

 A negatively charged ion is called an anion formed when an atom gains electrons

Cations vs Anions