Atomic Structure & Periodic Trends
What particles are found in the nucleus of an atom?
Protons and neutrons
What type of bond forms between two nonmetals?
Covalent bond
What assumption of the ideal gas law explains why gases expand to fill their container?
Gas particles have negligible volume and move randomly
What type of intermolecular force exists in all molecules?
London dispersion forces
What experimental factor increases reaction rate without changing activation energy?
Increasing concentration or surface area
Which periodic trend explains why atomic radius decreases from left to right across a period?
Increasing effective nuclear charge
What molecular geometry has bond angles closest to 120°?
Trigonal planar
At the same temperature, which gas has the highest average molecular speed?
The gas with the lowest molar mass
Why do larger molecules generally have higher boiling points?
Stronger dispersion forces due to larger electron clouds
Why does increasing temperature increase reaction rate?
More particles have sufficient energy to overcome activation energy
Why does fluorine have a higher electron affinity (more negative value) than oxygen?
An added electron completes fluorine’s valence shell, increasing stability
Why does HF have a much higher boiling point than F₂?
HF exhibits hydrogen bonding; F₂ only has dispersion forces
Why does real gas behavior deviate most at high pressure?
Gas particles are closer together, increasing intermolecular attractions
Which intermolecular force is responsible for water’s unusually high boiling point?
Hydrogen bonding
How can spectrophotometry be used to determine solution concentration?
By comparing absorbance to a calibration curve (Beer’s Law)
Which atom has the lowest first ionization energy and why?
An alkali metal, because its valence electron is far from the nucleus and weakly held
What does resonance indicate about bonding in molecules like O₃ or NO₃⁻?
Electrons are delocalized and bonds are equivalent in length
Why does helium behave more ideally than nitrogen under the same conditions?
Helium is smaller and has weaker intermolecular forces
Why does pentane have a lower boiling point than hexane?
Pentane has weaker dispersion forces due to smaller size
Why does doubling the concentration of a reactant quadruple the reaction rate in some reactions?
The reaction is second order with respect to that reactant
Why is there a large jump between the second and third ionization energies for Group 2 elements?
The third electron removed comes from a core shell, requiring much more energy
Why is the Lewis structure with the lowest formal charges considered most accurate?
It represents the most stable electron distribution
When the number of moles of gas doubles in a rigid container at constant temperature, what happens to the pressure?
The pressure doubles
Why do polar and nonpolar substances often fail to mix?
Their intermolecular forces are incompatible (“like dissolves like”)
Why does a reaction with a large activation energy proceed slowly at room temperature?
Few collisions have enough energy to form products