Chapter 14 Periodic Trends CHM2046

Similar to Group 1 Elements, Hydrogen has an outer electron configuration of ___ and is most commonly a ____ oxidation state.

ns^1 and +1

However, unlike the Group 1 elements, Hydrogen has what type of relationship with valence electrons.

Hydrogen shares its single valence electron with nonmetals rather than transferring it to them.

When comparing hydrogen to the group 1 elements, who has the higher ionization energy and electronegativity?

Hydrogen

For example: Lithium has an IE of only 520 kJ/mol, while hydrogen has 1311 kJ/mol. Additionally, hydrogen has the highest EN of the alkali metals.

Similar to the Group 14 elements, hydrogen shares what type of properties? (hint there are 5 described in the book)

Half-filled valence, Ionization energy, electronegativity, electron affinity, and bond energy similar to Group 14.

What is a key difference between the Group 14 elements and Hydrogen?

Although hydrogen’s valence level is half filled (like the group 14), there is only ONE electron in it.

Like the Group 17, Hydrogen has the following properties

occurs as a diatomic molecules and fills its outer level by sharing or gaining one electron from a metal.

When hydrogen share or gain one electron from a metal, it forms a 1- ion which is called a

hydride

Unlike the Group 17 elements, the halogens and hydrogen differ in the fact that

the monatomic halide ions are common and stable, while H- is rare and reactive. And hydrogen has a lower EN. And lacks 3 valence electron pairs

Hydrogen’s unique behavior arise from its

tiny size

The reason why Hydrogen has a high IE is because

hydrogen’s electron is very close to the nucleus and with no inner electrons to shield it from the positive charge

The reason why Hydrogen has a low EN (for a nonmetal) is because

it has only one proton to attract bonding electrons

The ______ the isotope is, the _____ the molar mass of the molecule, melting/boiling point, and heats of phase change.

higher;higher

Elemental hydrogen forms three types of hydrides:

ionic, covalent, and metallic

Protium

one proton, one electron surrounding it

deuterium

one proton, one neutron, and one electron

tritium

one proton, two neutron, and one electron

Ionic (saltlike) hydrides are formed when

reactive metals from group 1 or larger members of group 2 react with hydrogen

ex: 2Li (s) + H2 (g) —> 2LiH (s)

In water, H- acts as a strong base that pulls H+ from surrounding H2O molecules to form…

Given NaH + H2O ——>

H2 and OH-

Covalent Hydrides are formed when hydrogen reacts with

nonmetals

In most covalent hydrides, hydrogen has an oxidation number of +1, this is because

the other nonmetal has a higher electronegativity

When preparing covalent hydrides, for the stable, triple bonded N2, hydrogen reacts at (what type of conditions must take place)

high temperatures, high pressures, and the reaction needs a catalyst.

On the other hand, with reactive and single-bonded F2 and hydrogen, the reaction is often

occurring even at extremely low temperatures

Metallic (interstitial) hydrides are formed when

H2 molecules occupy the holes in the transition element/metal’s crystal structure.

The hydrides formed in metallic (interstitial) are not compound but rather __________. And they do not have a specific stoichiometric formula because the metal can incorporate variable amounts of hydrogen.

gas-solid solutions

What are the period 2 elements. (yes u can look at ur periodic table)

lithium (Li), beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), and neon (Ne)

Electrons of period 2 occupy in the

1 ns and 3 np orbitals

As you go across period 2, the nuclear charge increases due to the

addition of electrons to the orbitals of the same energy level (same n value)

As you go across period 2 (and most period) the atomic size ______ whereas first ionization energy and electronegativity ____.

decrease; increase

Metallic character _____ across the period this is because the nuclear charge increase and it switches from metals to metalloids to nm,

decrease

Where is reactivity highest? And give examples of specific groups.

Reactivity is highest at the left and right ends of the periods (except for noble gas) examples include Group 1 and 17

With Period 2, bonding between an active nonmetal will change from (as you go across period 2)

ionic, polar, covalent, to covalent

With period 2, bonding between an metal changes from

metallic, to polar covalent, to ionic

What are some characteristics that Alkali metals have that are unique for metals? (there is three in particular)

1) Unusually soft and easily cut

2) Lower melting and boiling points than any other group of metals

3) Lower densities than most metals

The unusual physical behavior of these metals can be traced to what

the largest atomic size in their respective periods and the ns1 configuration

Since the single valence electron (ns1) in the alkali metals are relatively far from the nucleus, what occurs? And why is this important in explaining the bonding strength.

only weak attractions exist in the solid between the delocalized electrons and metal-ion cores. Weak bonding = easily broken down and thus the low melting point and soft consistency

Alkali metals are reactive and since the outer electron is lost during reactions, alkali metals are powerful (reducing or oxidizing agent)?

Remember: OIL RIG

powerful reducing agent

Alkali metals reduce halogens to form ________ in highly exothermic reactions

E (s) + X2 —————> EX2 (s)

ionic solids

Alkali metals reduce hydrogen in water (reacting vigorously) to form ____ and a ______ hydroxide solution

2E (s) + 2H2O ——>

H2 and metal

Note that H2O is being reduced to H2 (from oxidation state of +1 to 0) since H2 elemental state is 0 for ON

Alkali metals reduce molecular hydrogen to form _____ hydrides

2E (s) + H2 ——>

ionic

Alkali metals form _____ by reducing O2 in the air.

oxides

Steps for the reaction between alkali metal and nonmetal

atomization, ionization, and lattice formation

atomization (between a reaction of alkali metal and nm)

The solid metal separates into gas atoms. Since it is weak metallic bonding, the separation needs low value of ΔH. This also decreases down the group

E(s) ——> E (g)

Ionization (between a reaction of alkali metal and nm)

the metal atom transfers its outer electron to the nm. Alkali has low IE and forms cations with small radii.

Group 1 ions are small spheres with considerable charge density.

Lattice formation

the resulting cations and anions attract each other to form an ionic solid.

Group 1 salts have high lattice energies

As cation radius increases, the lattice energy______.

Notice that since the cations of alkali metals are small, the lattice energy is large.

decreases

Despite the strong ionic attractions (high lattice energy), the salt are water soluble this is because

attraction between the ions and water molecules creates highly exothermic heat of hydration and a large increase in entropy when dispersed and hydrated occurs, this outweighs high lattice energy

Magnitude Hydration energy decreases as ionic size ______

increases

magnitude basically means forget the neg and focus on overall

rank the magnitude of hydration energy of group 1 given that it decreases as ionic size increase

look at periodic table of group 1 and rank decreasing hydration energy

Li > Na > K > Rb > Cs

given weaker bonds equals lower delta H, rank group 1 in decreasing ΔH

Li > Na > K > Rb > Cs

smaller ions form ____ hydrated ions

larger

The differences between group 1 and group 2 are all rooted on

the change in outer electron configuration from ns1 to ns2

When comparing group 1 and group 2, who has the higher melting point and boiling point?

group 2

Group 2 have ____ atomic radii and _____ ionization energy than Group 1.

smaller; larger

Even though group 2 does have more valence electrons, so why is Zeff still extremely large?

the second electron lies in the same sublevel, so it is not shielded very well

Alkaline earth metals are ____ agents.

reducing

Each alkaline earth metal reduces O2 to form a oxide, EXCEPT FOR

Be and Mg. they form adherent oxide coatings and reduces H2O instead

Alkaline earth metals also reduce ______ such as N2 and H2 to form ionic compounds. Except Be.

halogens

The oxides of metals such as alkaline earth metals are strongly ____ (acidic or basic)?

And what is the exception?

basic

amphoteric BeO

Basic Oxides react with acidic oxides to form _____

salts, such as sulfites and carbonates

What does reacting SrO (s) + CO2 (g) ——> yield?

(look at reactants)

SrCO3, a salt carbonate

Elements in group 2 are highly reactive because of their high lattice energies. Given that Group 2 alkaline earth metal cations are smaller and doubly charged compared to Group 1 elements, what can be inferred about their charge densities and lattice energies?

A. Higher charge density and higher lattice energy.

B. Higher charge density and lower lattice energy.

C. Lower charge density and higher lattice energy.

D. Lower charge density and lower lattice energy.

A. Higher charge density and higher lattice energy.

Higher lattice energy leads to ______ solubility of Group 2 salts in water.

lower

Higher charge density increases heat of hydration, but what does it increase more of?

Lattice energy

What happens to melting point and densities down a group of metals

melting point decreases and densities increase

Reactions: Alkaline metals reduce O2 to form oxides

2E(s) + O2 (g) ————> 2EO(s)

Reactions: Ba forms peroxide

Ba (s) + O2 (g)————— > BaO2 (s)

Reaction: Larger metals reduce water to form hydrogen gas, such as Ca, Sr, Ba

E(s) + 2H2O (l) ————> E²+ 2OH- + H2 (g)

Reaction: Metals reduce halogens to form ionic halides (use E for alkaline earth metals and X to describe halogens)

except for Be

E(s) + X2———> EX2(s)

Reaction: Metals reduce hydrogen to form ionic hydrides

except for Be

E(s) + H2 (g) ————→ EH2 (s)

Group 13, Boron family includes elements of

Boron, Al, Ga, In, Tl, and synthesized Nh

Because the d and f block in included in the heavier members of group 13 such as Ga, In, and Tl have nuclei with many more protons but Zeff is larger since

d and f electrons penetrate very little, and are poorly shielded from the higher positive charges

Since the heavier members of the boron group has a stronger nuclear pull (greater Zeff), they have _____ atomic radii and ___ ionization energies.

smaller and larger

In the Boron Group, Boron is a ______ with the characteristics of

network covalent metalloid; black, hard, and very high melting

Other group members in the Boron group are _____ with the characteristics of

metals; shiny and relatively soft with low melting

Aluminum makes a great conductor because of it’s

low density and three valence electrons

Fun Fact: Gallium’s metallic bonding gives it the largest liquid temperature range of any element. It melts at skin temperature, but does not boil until 2403 Celsius

yay

Boron is the only metalloid, this means that it is

A) More reactive at room temperature than the other members and have a softer exterior

B) More reactive at room temperature than the other members and form ionic bonds exclusively

C) Less reactive at room temperature than the other members and forms covalent bonds exclusively

D) Less reactive at room temperature than the other members and forms ionic bonds exclusively

E) Less reactive at room temperature than the other members and do not form any bonds to it’s metalloid behavior

C) Less reactive at room temperature than the other members and forms covalent bonds exclusively

Although Aluminum acts like a metal physically, its halides exist in the gas phase as _________.

covalent dimers

covalent dimers

molecules formed by joining two identical smaller molecules and its oxide is amphoteric rather than basic

Excluding boron, most other Group 13 compounds are considered ionic. However, what unique characteristic of their cations leads to a significant covalent character in these compounds?

A. They are predominantly ionic due to their triple charge, with minimal covalent character.

B. Their large size and triple charge prevent effective polarization, making them purely ionic.

C. While mostly ionic, their small, triply charged cations effectively polarize anions, giving their compounds more covalent character.

D. They are exclusively covalent compounds, similar to boron.

C. While mostly ionic, their small, triply charged cations effectively polarize anions, giving their compounds more covalent character.

The redox behavior of group 13 exhibits three features that appear here first and later in group 14/16:

1) Presence of multiple oxidation states

2) Increasing stability of the LOWER oxidation state

3) Increasing metallic behavior and basicity of oxides

Group 13 exhibits oxidation number of +3 (three outer electrons). Large members also have a oxidation state of +1, because

this occurs when the atoms lose their np electrons only and not ns

Because of the lower oxidation state, increase of stability increases as it goes down a group, examples include ____, ___, ____ that have a +1

Ga, In, and Tl

When you increase metallic character, the basicity of oxides increase. Is In2O or In2O3 more basic?

In2O, lower oxidation state

Boron forms network covalent compounds and large molecules. What is the unifying feature of many boron compounds, and what two strategies does boron commonly employ to complete its outer electron shell?

A. It forms primarily ionic bonds to achieve an octet, accepting electrons from metals.

B. Its electron deficiency is addressed by forming network covalent compounds, primarily through accepting electron pairs or forming bridge bonds.

C. It achieves electron saturation by donating its electrons to highly electronegative atoms, forming stable molecules.

D.Boron is electron rich and forms stable compounds by donating electrons to non-metals.

B. Its electron deficiency is addressed by forming network covalent compounds, primarily through accepting electron pairs or forming bridge bonds

Gaseous boron tri-halides, Boron is electron deficient in this compound, to attain an octet it can accept a lone pair. For example, write the equation for BF3 and NH3

BF3 + NH3 ———> F3B—NH3 (g)

Boric acid or B(OH)3. Write the reaction between Boric acid and water.

Hint: boron’s two way of fulfilling itself is either accepting lone pairs or forming bridge bonds. So what will it take from water?

B(OH)3 (s) + H2O (l) ———> B(OH)4- + H+

In elemental Boron and hydrides called Boranes, there is no electron rich atom, so they are supplied via unusual bonding called bridge bond which occurs when

three-center, two-electron bond

Each B——H——B is held together by only ___ electrons

two

What elements are in the Carbon Family (group 14)? List the elements down a group and show what properties that each have.

Nonmetallic carbon, metalloids Si and Ge, metallic Sn and Pb, and Fl

What is the electron configuration of Group 14? Down the group, the number of oxidation state ______ and the lower +2 state becomes more common.

ns2np2. oxidation stat edecreases

The elements of Group 14 and their neighbors in Groups 13 and 15 illustrate how some physical properties depend on the _______ in an element.

types of bonding

Network covalent solids such as B, C, Si, Ge, As, and Sb have a higher _________ and ΔH values than metallic solids?

melting point

However, metallic solids have ________ (higher or lower) values than N and P. This is because N and P exist as

higher. they exist has individual covalent molecules

Who has lower melting point and why. Compare C and Si

Si has a large decrease in melting point because longer, weaker bonds in the Si structure.

Large decrease between Ge and Sn is due to the change from _____ to ______ bonding.

covalent network to metallic

Horizontal trend shows _____ in melting point and ΔH across a period.

increase

Reactions: group 14 elements are oxidized by halogens

E(s) + 2 X₂ ^———> EX₄

The +2 halides are more stable for

tin and lead