Atomic Radius
Why does atomic radius decrease across a period even though electrons are added?
The increasing number of protons raises the effective nuclear charge, pulling electrons closer while shielding remains nearly constant.
Why does ionization energy increase across a period?
Effective nuclear charge increases, holding electrons more tightly.
Why does electronegativity increase across a period?
Stronger nuclear charge and smaller radius increase attraction for bonding electrons.
Why do alkali metals become more reactive down a group?
Their valence electron is farther from the nucleus and more shielded, so it is lost more easily, increasing reactivity.
Why do elements in the same family have similar chemical properties?
They have the same number of valence electrons, which determines how they bond and react.
Why does atomic radius increase down a group?
Additional energy levels are added, increasing electron distance and shielding, which outweighs nuclear attraction.
Why does ionization energy decrease down a group?
Increased distance and shielding make electrons easier to remove.
Why does electronegativity decrease down a group?
Increased shielding and distance weaken the nucleus’s pull on bonding electrons.
Why do halogens become less reactive down a group?
Their ability to gain an electron decreases due to increased atomic radius and shielding, weakening nuclear attraction.
Why are alkali metals highly reactive and form +1 ions?
They have one valence electron that is easily lost, resulting in a stable noble gas configuration.
Why are cations smaller than their neutral atoms?
Losing electrons reduces electron-electron repulsion and may remove an entire energy level, allowing the nucleus to pull remaining electrons closer.
Why is there a drop in ionization energy between Group 2 and Group 13 elements?
The electron removed from Group 13 is in a higher-energy p orbital, which is less tightly held than an s orbital.
Why is fluorine the most electronegative element?
It has a very small radius and high effective nuclear charge, maximizing attraction for electrons.
Why are metals and nonmetals reactive in opposite ways?
Metals react by losing electrons (low ionization energy), while nonmetals react by gaining electrons (high electronegativity).
Why do alkaline earth metals form +2 ions instead of +1?
They have two valence electrons, and losing both leads to a stable electron configuration.
Why are anions larger than their neutral atoms?
Gaining electrons increases repulsion among electrons, expanding the electron cloud.
Why does removing a second electron require more energy than the first?
After removing one electron, the ion becomes positively charged, increasing attraction to remaining electrons.
Why do metals generally have low electronegativity?
They tend to lose electrons rather than attract them.
Why is fluorine more reactive than chlorine?
Fluorine has a smaller radius and stronger attraction for electrons, making it more effective at gaining electrons in reactions.
Why do halogens typically form −1 ions?
They need one additional electron to complete their valence shell, making electron gain favorable.
Why do elements in the same group have similar chemical behavior despite different radii?
They have the same number of valence electrons, which primarily determines chemical reactivity.
Why do noble gases have very high ionization energies?
Their full valence shells are very stable, making electron removal difficult.
Why does electronegativity influence bond type?
Larger differences lead to ionic bonds, while smaller differences result in covalent bonds.
Why are noble gases generally unreactive?
Their valence shells are full, making them energetically stable and unlikely to gain or lose electrons.
Why do transition metals show variable oxidation states?
Their d orbitals can participate in bonding, allowing different numbers of electrons to be lost or shared.