3.6-3.8 Periodic Trends- Atomic/Ionic Radius, Ionization Energy, Electron Affinity, Metallic Character

For Main Group elements, the atomic radius ______ left to right across a period

DECREASES

why do atoms get smaller across a period?

adding more protons to the nucleus makes it more positively charged.

more protons = stronger nucleus = pulling electron cloud inward tightly =

smaller atom

for Main group and Transition elements, the atomic radius _____ down a group

INCREASES

why do atoms get larger down a group?

Each row down means adding a completely new, higher principal energy level (𝑛-shell)

more n-shells = further electrons =

bigger atom

Effective nuclear charge (Z_eff)

the net positive charge an electron actually feels from the nucleus

the nucleus is positive and therefore ____ on negative electrons

PULLS

During shielding, because inner electrons block the nucleus, what happens to the outer electrons?

they do not get the full positive pull

What happens to outer electrons that get shielded by core electrons in their way?

they feel a LESSER effective nuclear charge

more shielding = ____ Z_eff

LESS

During penetration, when the electron slips past the shield where does it go?

inside the inner electron cloud and right next to the nucleus

What happens to electrons that penetrate closer to the nucleus?

they feel a GREATER effective nuclear charge

more penetration = ____ Z_eff

MORE

cations have ______ radii than their neutral parent aroms

SMALLER

losing electrons make protons pull on less electrons, which make a _____ ___ ____

stronger nuclear pull

anions have ______ radii than their neutral parent aroms

LARGER

when electrons are added (anions), since like-charges repel, adding more electrons causes them to

push them away from eachother

what happens to the nuclear pull as electrons are gained?

it gets weaker

what happens when the nucleus cannot pull highly repelling electron cloud inward once electrons are gained?

the electron cloud swells and expands outward, increasing the radius/size

isoelectronic species

different atoms or ions that have the exact same number of electrons but different sizes/number of protons

when ions share the same number of electrons / same electron configuration, size entirely depends on the amount of…

PROTONS

more protons = ___ size

SMALLER

First Ionization Energy

the amount of energy required to completely remove an electron from a neutral atom in its gas phase

X(g) →

X⁺(g) + 1 e-

first ionization energy ______ left-to-right across a period for Main Group elements

INCREASES

Group 2A to 3A anomaly

e- in p-orbital easier to remove than e- in s-orbital

Group 5A to 6A anomaly

due to relieving repulsions between 2 e-’s occupying the same orbital

first ionization energy ______ top-to-down a group

DECREASES

As you move down any column on the periodic table, it becomes ______ to remove an electron

EASIER

metals have ___ ionization energies and lose electrons to become ______ easily

LOW, CATIONS

nonmetals have ____ ionization energies and resist ____ ______ —> gain them instead

HIGH, LOSING ELECTRONS

Successive Ionization Energies

the energy required to remove multiple electrons from the same atom, one after the other

it gets increasingly ______ to remove successive electrons

HARDER

a jump in ionization energy occurs after removing ___ ______

core electrons

Electron Affinity

the change in energy that happens when a neutral atom in the gas phase gains an electron to become a negative anion

X(g) + 1 e- →

X^-(g)

a negative energy value

a release of energy (exothermic electron affinities)

a positive value

requires energy (endothermic) because the atom resists taking it

Groups 2A, 5A, and 8A tend to have _____ electron affinities

positive

Groups 2A, 5A, 8A exception in electron affinity

these columns have filled or half-filled subshells that are already highly stable. Forcing an extra electron into them ruins that stability, so they have positive or near-zero electron affinities

Metallic Character

trend that describes how easily an atom can lose its outer valence electrons to behave like a typical metal.

metallic character ______ as you move toward the ____-__ corner of the periodic table

INCREASES, BOTTOM-LEFT

metals: typical physical state

usually solids (except Hg)

nonmentals: typical physical state

solids, liquids, gases

metals: appearance

lustrous and shiny

nonmetals: appearance

dull

metals: physical properties

high density

malleable

ductile

conducts heal well

conducts electrivity well

high melting and boiling points

nonmetals: physical properties

low density

brittle

conducts heat poorly

conducts electricity poorly

low melting and boiling points

metals: electron behavior**

lose electrons easily to form cations

nonmetals: electron behavior**

gain electrons easily to form anions