Inorganic 1 Topic 6

s and p block

… bonds are typically stronger than corresponding … bonds

heteronuclear, homonuclear

Amphoteric defjnition

can act as both an acid and a base

Effective nuclear charge definition

the net positive charge experienced by an electron in a multi-electron atom, accounting for both the nucleus and electron shielding effects

The … force between the nucleus and the electron in question is offset by … between the electron in question and all electrons …

attractive, repulsion, between

Electronegativity definition

the ability of an atom to attract electron density towards itself in a molecule

Electronegativity can lead to the … of a covalent bond

polarisation

A … bond with partial charges due to … is sometimes described as having … character

covalent, polarisation, ionic

Is electronegativity affected by oxidation state?

yes: a greater oxidation state results in greater Z_eff due to fewer electrons and less shielding

How does the electronegativity differ with respect to different hybridisation states?

sp > sp² > sp³ due to increased s character

Electronegativity depends on which four properties?

• effective nuclear charge (Z_eff)

• principal quantum number (n)

• oxidation state

• hybridisation

It is possible for a … to polarise an … in an ionic bond

cation, anion

An ionic bond in which the cation … the anion is described as having some … character

polarises, covalent

Definition of polarizability of an atom

its ability to be distorted by an electric field, such as that of a neighbouring atom

Atoms are … if their … can be distorted easily

polarisable, electron cloud

What type of cations have polarising ability

small and highly-charged

General properties of metals:

• electric and thermal conductors

• ductile

• malleable

• lustrous

• often form alloys

What type of oxides do metals form?

basic

General properties of non-metals:

• poor conductors of heat and electricity

• dull

• brittle

• lower density than metals

What type of oxides to non-metals form?

acidic

Electronegativity values of metals, metalloids, and non-metals:

Metal < 1.9

Metalloid = 1.9 - 2.2

Non-metal > 2.2

What are the requirements for something to be a metal?

• must have a partially filled band (band theory)

• electrons must be delocalised

Elements with … electronegativity have more … bound electrons in more … orbitals

lower, loosely, diffuse

In a metal, the … orbitals can easily … and therefore … can move easily

diffuse, overlap, electrons

Non-metals in the lower half of the periodic table are … in high oxidation states and … in low oxidation states

acidic, amphoteric

How does electronegativity relate to an element forming a basic or acidic oxide?

basic oxides: low electronegativity

acidic oxides: high electronegativity

amphoteric oxides: intermediate electronegativity

For the s- and p-block, the most important factor determining oxidations state is …

closed shell electronic configuration

Closed shell electronic configuration definition

a state in which all the atomic or molecular orbitals within a specific energy level (e.g. both 2s and 2p) are fully occupied with electrons

Atoms prefer to follow the … and have a …configuration

octet rule, noble gas

Groups in the p-block tend to have favoured …

oxidation states

The favoured oxidation state values in each group tend to vary by …

±2

For the common oxidation states in the p-block, the atoms tend to contain no …

unpaired electrons

The favoured oxidation state of an element in the p-block can … down the group

change

Inert pair effect definition

the tendency of the two outermost s-electrons being excluded from bonding (i.e. the element only uses its p-electrons in bonding), resulting in higher oxidation states becoming inaccessible

In hybridisation of carbon, an … is promoted to a …

s-electron, p-orbital

The energy required to promote an electron to a higher-energy orbital is called the …

promotion energy

For certain compounds, the energy … to … the s-electron is compensated for by the energy … in the formation of more … bonds

required, promote, gained, stronger

How do the electron promotion energies (s → p) change down the groups?

electron promotion energy increases down the group as the energy gap between s- and p-orbitals increase

How does the energy gain from more bond formation change going down a group?

the energy gain decreases as the atoms get larger and the bonds they form are weaker (so release less energy when they form)

Species with … positive oxidation states tend to be good … agents

high, oxidising

What are the effects of the high electronegativity of fluorine and oxygen in terms of being oxidised?

they are sufficiently electronegative to withstand the oxidising effect of species with a high oxidation state, such as in SO₃

High “formal charge” centres are good at … electrons

attracting

Bond energy definition

the amount of energy required to break a bond into neutral atoms, defined for all gaseous species

Mean bond enthalpy definition

the amount of energy required to break a given bond, averaged over a range of different compounds which contain that bond

Mean bond enthalpies allow us to … trends in typical bond energies across …

compare, multiple compounds

What is the general trend in the strength of homonuclear single bonds?

bonds get weaker as you go down the group

Why does the strength of a homonuclear single bond decrease down a group?

• atomic radii increase

• orbitals become larger and more diffuse

• there is poorer overlap between orbitals, resulting in a weaker interaction

Why are homonuclear single bonds between nitrogen, oxygen, and fluorine atoms particularly weak?

• N, O, and F are very small atoms

• the atoms sit very close together in a single bond

• the adjacent lone pairs experience significant repulsion

Why do carbon and boron not experience the same bond-weakening interaction as N, O, and F?

because they don’t have any lone pairs

Why are heteronuclear bonds stronger than homonuclear bonds?

there is a bigger difference in electronegativity in heteronuclear bonds, so there is a degree of strengthening ionic character

As the … difference between atoms in a … bond increases, the strength of the bond … due to … overlap between orbitals

size, heteronuclear, decreases, poorer

Why is the F-F bond weak?

• very short bond, repulsion of the positive nuclei

• lone pairs in close proximity to each other increases repulsion

• MO theory suggests highly-populated anti-bonding orbitals

Why is multiple bonding common in the first row of the p-block but not in other rows?

2p orbitals are small, so lateral overlap to form π orbitals is stronger

Catenation definition

when elements preferentially form lots of single bonds, generating polymer-like structures, rather than form multiple bonds

If sigma bonds are stronger than pi bonds, … bonds are more likely to form, and the species will be …

catenated, polymeric

If pi bonds are stronger than sigma bonds, … bonds are more likely to form, and the species will be …

multiple, molecular

Compounds in the second row of the p-block may display …

octet expansion

… involves attack by the … on the oxygen in water

hydrolysis, lone pair

Attack during hydrolysis requires an increase in … of the central atom

coordination atom

CCl₄ and SiCl₄ are … saturated and obey the …

coordinatively, octet rule

Explanation for the hydrolysis of SiCl₄

• silicon has empty 3d-orbitals, which are readily available and similar in energy

• these allow attack by oxygen lone pair

• silicon is a larger atom and there is more space around it for a water molecule to attack

• silicon is less sterically hindered

• silicon can expand its octet