Group characteristics + Periodic Trends

Alkali Metals

• ionization

• reactivity

• what compounds do they form

• Low ionization energies (easy to remove an electron from them) because they want to lose their outermost electron, so they can shift to the left and feel like the nearest noble gas. It’s a lot easier to shift left than right for elements in Group .

• Very reactive with water

• Readily form ionic compounds

Alkaline Earth Metals

• ionization

• reactions

• relationship with water

Alkaline earth metals (Group 2)

• Also have low ionization energies, but not as low as alkali metals

• Do react with H2O, but not as violently as the alkali metals

• Generally get more reactive with H2O as you go down the group

Halogens

• Electronegativity

• Electron Affinity

• Reactivity with what

Halogens (Group VIIA)

• High electronegativities and electron affinities (they have a high “thirst” for electrons)

• They are only one valence electron away from having a full octet.

• Thus, they are easily reduced and really want to have an extra electron.

• Highly reactive with metals, good oxidizing agents

Noble Gases

On the periodic table, there are certain groups that you should definitely know.

Noble Gases (Group VIIIA)

• Inert (unreactive) gases; they have a full octet and are happy.

Transition Metals (d-block)

• Often form brightly-colored compounds, due to the funky way that d-orbitals’ shapes allow their electrons to absorb colored light and be promoted to higher-energy levels

• Can have multiple oxidation states

Chalcogens

Oxygen group (Group VIA) – also called the “chalcogens”

• There are two forms of molecular oxygen: O2 and O3

• O2 is a good oxidizing agent (oxidant), and O3 is an even better oxidizing agent. (likes to steal electrons from other substances)

• Metals like to react with oxygen to form metal oxides.

With water

Oxidant

An oxidant (also called an oxidizing agent) is a substance that causes another substance to lose electrons during a chemical reaction.

In terms of Redox reaction:

• The oxidant gains electrons (so it is reduced).

• The other substance loses electrons (so it is oxidized).

What is a binary hydride

NaH

1 of each. NOT THE SECOND OPTION

Electron Affinity

• Exception

Energy released when an element accepts and electron


Cl IS MORE THAN F, which is odd, but an exception.

Bond Length vs Atomic Radius

Atomic Radius

An atom’s radius (called its atomic radius) is the distance from its nucleus to the

outside of its outermost orbitals.

Thus, an atom’s atomic radius helps convey the size of its electron cloud.

When two atoms bond, the distance between their nuclei is called their bond length.

For example . . .

For an H2 molecule, you can hopefully see that bond length = atomic radius × 2.

Bond length with different atoms

TREND FOR SIZE

SMALLER ON THE TOP RIGHT, BIGGER ON THE LEFT DOWN

RIGHT TO LEFT, more protons, more energy sucked in

• Protons ability to bring in electrons is called the effective nuclear charge

UP TO DOWN, more shells

What is an isoelectronic Series

• How to differentiate size between them

Atoms with the same number of electrons

AGAIN, the ones with the MOST PROTONS HERE, have the SMALLEST SIZE

Ionization Energy def + general trend

• Exception

Ionization energy is the amount of energy required to strip an electron from an atom. Even for elements like Na, which really want to get rid of their outermost it still takes energy to remove that electron.

GOES FROM RIGHT TO LEFT (MOST to LEAST)

UP TO DOWN (MOST TO LEAST)

F WANTS to keep the electron more than Fr

EXCEPTIONS

successive ionization energy

Believe it or not, it’s possible to remove more than one electron from atoms. An atom’s first ionization energy is the amount energy required to remove its first electron; its second ionization energy is the amount energy required to remove its second electron; and so forth

Each successive ionization energy (first, then second, then third, etc.) is larger than the previous one. So an atom’s first ionization energy is smaller than its second; its second is smaller than its third; and so on..

Once an atom “feels” like a noble gas, the ionization energy after that is REALLY big. Why? Because it feels like a noble gas! Once there, it doesn’t want to lose more

electrons.

EN

Atoms thirst for electrons, Right to up (more EN)

Electron Affinity

• EXCEPTIONS

If removing electrons costs energy, than adding electrons should produce

energy. And indeed, that is generally the case. The energy produced (or

given off) when an atom accepts an electron is called its electron affinity.

Electron affinity, then, is the opposite of ionization energy.

RIGHT TO UP.

exclude noble gases

BUT THERE IS EXCEPTIONS: F has the highest electron affinity, not Cl.

Be has a filled 2s subshell, so its electron affinity is around zero.

N has a half filled 2p subshell its electron affinity is around zero.