Experimental Evidence & Atomic Models
The subatomic particle whose exact quantity in the nucleus uniquely determines an element's atomic identity
What is a proton?
This form of radioactive decay emits a Helium-4 nucleus, reducing the parent mass number by 4 and atomic number by 2
What is Alpha Decay?
This light isotope serves as the primary nuclear fuel consumed during main-sequence stellar fusion
What is Hydrogen-1?
Excluding noble gases, this element located in Group 17 exhibits the highest electronegativity value (4.0) on the periodic table
What is Fluorine (F)?
A neutral Period 3 halogen like Chlorine has 7 valence electrons, giving it this specific count of core electrons
What is 10 core electrons?
Number of neutrons and electrons in Carbon-14
What is 8 neutrons and 6 electrons?
When an unstable neutron converts into a proton and ejects a high-speed electron, the atom undergoes this decay mode
What is Beta-minus decay?
The solar proton-proton chain fuses four Hydrogen-1 nuclei to produce energy, positrons, gamma rays, and one atom of this daughter isotope
What is Helium-4?
Moving left to right across Period 3 causes this atomic dimension to decrease due to increasing effective nuclear charge (Zeff)
What is Atomic Radius?
A massive spike in successive ionization energy between IE 1 (496 kJ/mol) and IE 2 (4,562 kJ/mol) identifies an element from this periodic group
What is Group 1?
The primary attractive force that holds atomic nuclei together and prevents electrostatic repulsion from driving protons apart
What is the strong nuclear interaction?
Light isotopes with an N/Z ratio higher than 1.0 sit above this stability belt, prompting beta decay to restore equilibrium
What is the Band of Stability?
Sitting at the absolute peak of the binding energy per nucleon curve, this nuclide represents the most stable atomic nucleus in the universe
What is Iron-56?
These electrons occupy the outermost principal energy level (n) and dictate an element's chemical reactivity and bonding
What are valence electrons?
Unstable nuclei with an N/Z ratio below 1.0 stabilize by converting a proton to a neutron via emission of this positive antiparticle
What is Positron emission?
Ernest Rutherford's experiment and the model that was developed
What is Gold Foil Experiment and Nuclear Model?
If a 100.0 g radioactive sample decays down to 12.5 g over 12.0 hours, this is the isotope's half-life in hours
What is 4.0 hours?
Fusing light nuclei with mass numbers under 56 releases massive energy because the reaction is of this thermodynamic classification
What is exothermic?
Calculated with the expression Z - S, this value represents the net attractive force valence electrons feel from the nucleus
What is Effective Nuclear Charge?
Between Magnesium (Z=12) and Sulfur (Z=16), this Period 3 element holds a higher Zeff (+6) and a noticeably smaller atomic radius
What is Sulfur (S)?
James Chadwick's experiment and the part of the atomic model that was improved through his experiment
In nuclear medicine, this combined metric accounts for both radioactive decay and biological elimination to determine net clearing rate
What is effective half-life (teff)?
Main-sequence stars cannot fuse elements heavier than Iron-56; those heavy elements are synthesized during these violent cosmic events
What are Supernovae (supernova explosions)?
Moving top to bottom down Group 1 causes First Ionization Energy to undergo this overall trend due to increased electron shielding
What is a decrease (it decreases)?
Attempting to fuse nuclei heavier than Iron-56 (A > 56) requires net energy input because the process is of this thermodynamic type
What is endothermic?