4.4 Atomic Structure

4.4 Atomic Structure

1. Parts of an atom

   • proton
     • in the nucleus
     • relative mass is 1
     • +1 charge
   • neutron
     • in the nucleus
     • relative mass is 1
     • neutral/ no charge
   • electron
     • size is negligible
     • -1 Charge
     • Orbiting the nucleus

2. Mass Number

   • Number of protons + neutrons in an atom
   • It can also be described as the number of neutrons of that atom added to the atomic number it gives its atomic mass number.

3. Isotope

   • each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties; in particular, a radioactive form of an element.

4. Half Life

   • the time taken for the radioactivity of a specified isotope to fall to half its original value