AP Chemistry : Periodic Trends
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Example Question #31 : Periodic Trends
Which of the following species has the largest radius?
Each of these species has the same electron configuration (that of 
Example Question #51 : The Periodic Table
Where are the largest neutral atoms found on the periodic table?
Bottom right
Top right
Top left
Bottom left
Bottom left
From left to right on the periodic table, atomic radius decreases because the number of protons increase while electrons are being added to the same shell; the attraction between the nucleus and the electron cloud override the shielding effect of adding electrons to the same shell. Therefore, those on the left are larger. From top to bottom on the periodic table, atomic radius/size increases because electrons are added to new valence shells significantly further from the nucleus than the previous shell. Therefore, those on the bottom left are largest.
Example Question #72 : Elements And Atoms
Which atom has a smaller atomic radius than oxygen?
Lithium
Fluorine
Nitrogen
Sulfur
Fluorine
From left to right on the periodic table, atomic radius decreases because the number of protons increase while electrons are being added to the same shell; the attraction between the nucleus and the electron cloud override the shielding effect of adding electrons to the same shell. Therefore, those on the left are larger. From top to bottom on the periodic table, atomic radius/size increases because electrons are added to new valence shells significantly further from the nucleus than the previous shell. Therefore, those on the bottom left are largest. Sulfur is the largest since it is in period 3. The remaining atoms are in period 2, with lithium being the largest, followed by nitrogen, oxygen, and fluorine.
Example Question #31 : Periodic Trends
An atom in which of the following groups is most likely to lose an electron?
Alkaline earth metals
Halogens
Noble gases
Alkali metals
Alkali metals
The tendency to lose an electron is related to ionization energy, which is principally the opposite of electronegativity. The higher the ionization energy, the harder it is to pull an electron from the atom (takes more energy to ionize). Elements on the right side of the periodic table have higher ionization energies because they tend to gain electrons to achieve a full valence electron shell rather than lose them. Elements on the left side of the periodic table have lower ionization energies because they tend to lose electrons in their valence shell to achieve a full shell. Alkali metals need to lose 1 electron to achieve noble gas electron configuration, whereas the first electron lost from an alkaline earth metal does not confer this stability.
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