chapter 8 Flashcards
what are electrons attracted to? repelled by?
attracted to nucleus and repelled by each other
what is shielding?
outer electrons (valence) are shielded from the nucleus by core electrons (feel a smaller net charge)
do electrons in the outermost orbitals shield each other?
Electrons in the outermost orbitals do not effectively
shield each other from the nuclear charge
what is effective nuclear charge? what do Z and S represent?
The effective nuclear charge is net positive charge
that is attracting a particular electron Z is the nuclear charge
• S is the shielding
constant
how can Zeffective be found?
Zeffective = Z − S
what are trends in radii controlled by?
Trends in the radii of neutral atoms, cations, and anions
is controlled by the effective nuclear charge (Zeff)
what happens as we move left to right across a period?
the effective nuclear charge increases as more protons are added to the nucleus (Z increases)
what can increase Z? what happens to S?
Adding more protons increases Z, while the shielding
constant, S, remains the same for the valence
electrons, therefore Zeff must increase
what happens to Zeffective as we move down a group? why?
As you move down a group, the effective nuclear
charge slightly decreases (minimal) : more core
electrons and shielding the same number of valence
electrons
what happens to the atomic radius as you move right across the periodic table? down a group?
Atomic radius decreases as you move right across the
periodic table
• Atomic radius increases as you move down a group
what happens to the atomic radius as we move across a period (left to right)?
Atomic Radius
Decreases across
period (left to right)
what happens as atomic radius decreases?
adding electrons to same valence shell - effective nuclear charge increases - valence shell held closer
what happens to the atomic radius as we go down a group?
Atomic Radius
Increases down group
what happens as atomic radius increases?
valence shell farther from
nucleus
- effective nuclear charge
fairly close
do transition metals follow trend? what do they do?
The atomic radius of transition metals do not follow the trend - Tend to stay constant across the d-block
what happens to Zeffective for transition metals? when electrons are added?
number of electrons in outermost level ?
The overall Zeff does not change much between transition metals. - As one additional e- is added to the d-orbital, another proton is added to the nucleus - The number of electrons in the outermost principal energy level stays the same (ns)
what are the d electrons considered for transition metals?
core electrons. will shield each other more so than main group valence/outer shell, so Zeff is more constant.
are cations smaller or larger than corresponding atoms? what trend do they follow?
• Cations are smaller than their corresponding atoms • Same trends for cations as atoms as you move across a row or down a group • Fewer electron repulsions
are anions smaller or larger? electron repulsion?
Anions are larger than their corresponding atoms • More electrons increase repulsions so the radii is larger
describe isoelectronic species (3 points)
The same number of electrons
• Can be a mix of cations/anions/noble gas
• Need to consider the number of electrons vs protons
for each species in order to determine which is
larger/smaller
what is ionization energy?
exothermic or endothermic?
Energy required to remove an electron
from an atom or ion in the gaseous state
Endothermic process, energy is always
positive
which electrons are easiest to remove? what is the ionization energy trend? exceptions?
• Valence electrons are the easiest to remove • Generally increase as we move across a period (rows) and decreases down a group • Except between 2A & 3A, and 5A & 6A
is more or less energy required to remove successive electrons?
Removal of each successive electron requires more energy • Cation gets smaller and electrons are held tighter
do valence or core electrons in full subshells have more energy? energy required to remove? why the difference?
• Core electrons which are in full subshells
are much lower in energy than the valence
shell electrons
• A lot more energy is required to remove
core electrons compared with valence
electrons
• The large jump in ionization energies
occurs between the removal of valence
electrons and core electrons
what happens when a neutral atom gains an electron? what is electron affinity?
• Energy released when a neutral atom gains an electron
to form an anion
• Exothermic reaction
Fundamentally opposite of ionization energy
what happens to affinity as we move across rows?
Affinity increases as we move across rows in the
periodic table
• Zeff is larger as we move across a period so there is a
greater attractive force between the added electron and
the nucleus, resulting in more energy being released
trends of metallic character? (3 points)
Metals tend to lose electrons in chemical reactions
• As we move across the rows metallic character
decreases
• As we move down groups the metallic character
increases
