Predicting the behavior of the various elements and compounds that exist in nature allows us to make inferences about their interactions or properties. Our many models and theories allow us to better understand and predict the microscopic world around us. Welcome to Falcon Online's AP Chemistry, where we will take you on a journey to understanding the basics of advanced level chemistry.
But, every journey must begin from somewhere, and there is no better way to start this one than by starting from single atoms, and properties of simple elements..
Let's understand the the various interactions that govern elemental properties, including atomic radius, shielding, ionization energy, and electronegativity.
TERMS AND DEFINITIONS
Z Effective Nuclear Charge: Net positive charge that the nucleus exerts on the electrons in the electron cloud. The "nuclear pull".
Atomic Radius: The size of the atom from the center of the atom to the outermost electron shell.
Nth Ionization Energy: The amount of energy needed to remove the nth outermost electron from the atom
Electronegativity: How strongly an atom can pull bonding electrons closer to itself in a compound.
Shielding: The ability for innermost electrons to push away outer electrons and decrease the pull of the nucleus on outer electrons.
PERIODIC TABLE of ELEMENTS for REFERENCE:
Atomic Radius Decreases Left to Right: The effective nuclear charge of elements increases from left to right in a periodic table, as the number of protons increases. Thus, as the effective nuclear charge increases, the electrons in the atom penetrate closer to the nucleus, and this decreases atomic radius
Atomic Radius Increases Top to Bottom: The number of electron shells in an atom increases from top to bottom, and as there are more shells, the size of the atom itself must increase. Thus, as the number of electron shells increases, so does atomic radius.
Ionization Energy Decreases Toward the Bottom and To the Left: The greater number of electron shells in an atom increase the amount of shielding in an atom, thus decreasing the ionization energy of atoms. Furthermore, towards the left the atomic radii are larger, so the effects of nuclear pull are less. Therefore, the ionization energy decreases toward the bottom left.
Electronegativity Increases Toward the Top and To the Right: The greater amounts of protons in the nucleus increases effective nuclear charge, and a smaller atomic radius near the top increases the attraction toward the bonding electrons. Therefore, Elecronegativity increases heading towards the top right.
Exceptions to Periodic Trends: Due to the effects of electron electron repulsion, adding an electron to the p orbital in the Boron group decreases the ionization energy rather than increasing it. And again, due to the electron electron repulsion in the Oxygen group, adding an electron and doubling an otherwise unpaired electrons in a half filled structure increases electron electron repulsions, thus making it easier to remove an electron.
Thanks for Reading! Be sure to keep an eye out for future blog posts or videos! Happy Studying!
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