Chapter 5 - Electrons and bonding

Question 1

What are shells regarded as?

Answer 1

Shells are regarded as energy levels and the energy increases as the shell number increases.

Question 2

What is the shell number or energy level number called?

Answer 2

The principle quantum number n.

Question 3

What is the maximum number of electrons a shell n can hold?

Answer 3

Number of electrons: 2n^2.

Question 4

What are shells made up of?

Answer 4

Shells are made up of atomic orbitals.

Question 5

What is an atomic orbital?

Answer 5

An atomic orbital is a region around the nucleus that can hold up to two electrons, with opposite spin. Models visualise an atomic orbital as a region of space where there is a high probability of finding an electron.

Question 6

What is the maximum number of electrons an orbital can hold?

Answer 6

An orbital can hold two electrons at most.

Question 7

What are the different types of orbitals?

Answer 7

S-, p-, d- and f- orbitals.

Question 8

What is the shape of an S orbital and what happens as the shell number increases?

Answer 8

In an s orbital the electron cloud is within the shape of a sphere. As with all orbitals, an s-orbital can hold one or two electrons. Each shell from n=1 contains one s orbital and the greater the shell number n, the greater the radius of its s orbital.

Question 9

What is the shape of an P orbital and what happens as the shell number increases?

Answer 9

a. In a p orbital, the electron cloud is within the shape of a dumb-bell. As with an s-orbital, one orbital can contain up to two electrons. There are three separate p orbitals at right angles to one another. These orbitals are referred to as Px, Py, and Pz.
b. Each shell from n=2 contains three p orbitals and the greater the shell number n, the further the p orbital is from the nucleus.

Question 10

What are the properties of d- and f-orbitals?

Answer 10

a. Each shell from n=3 contains five d orbitals.

b. Each shell from n=4 contains seven f-orbitals.

Question 11

Within a shell what are orbitals of the same type grouped together as?

Answer 11

They are grouped together as sub-shells.

Question 12

What does each new shell gain in terms of orbitals?

Answer 12

Each new shell gains a new type of orbital.

Question 13

How does an orbital fill within a shell?

Answer 13

Within each shell, the new type of sub-shell added has a higher energy. For example, in the second shell, the 2p sub-shell is the new type, and is at a higher energy than the 2s sub-shell.

Question 14

In the third shell what is the highest energy level, and does it overlap with any orbitals in the fourth shell?

Answer 14

The 3d subshell is at a higher energy level than the 4s sub shell. The 4s subshell therefore fills before the 3d subshell. The order of filling is therefore 3p, 4s, 3d.

Question 15

What property do electrons have and how is this displayed in an orbital?

Answer 15

Electrons have a property called spin – either up or down. The two electrons in an orbital must have opposite spins. The opposite spins help to counteract the repulsion between the negative charges of the two electrons.

Question 16

Should electron configurations be shown in shell order or the order of filling?

Answer 16

Should be shown in shell order.

Question 17

Why is the periodic table divided into s, p and d blocks?

Answer 17

a. The periodic table can be divided into blocks corresponding to the highest energy sub-shell.
b. Within the s-block the highest energy electrons are in the s-sub-shell.
c. Within the p-block the highest energy electrons are in the p-sub-shell.
d. Within the d-block the highest energy electrons are in the d-sub-shell.

Question 18

When forming ions how can you alter the electron configuration?

Answer 18

When forming ions, the highest energy sub-shells lose or gain electrons.

Question 19

What happens when forming ions of the d-block elements?

Answer 19

The 4s subshell is initially at a lower energy state than the 3d sub-shell, so is filled first. However, once filled the 3d energy level falls below the 4s energy level. Therefore, the 4s electrons are first in and the 4s electrons are first out.

Question 20

What is ionic bonding?

Answer 20

Ionic bonding is the electrostatic attraction between positive and negative ions. It holds together cations and anions in ionic compounds.

Question 21

In which directions do ions attract in ionic bonding?

Answer 21

Each ion attracts oppositely charged ions in all directions.

Question 22

What structure does ionic bonding result in?

Answer 22

Ionic bonding results in a giant ionic lattice structure containing billions and billions of ions, the actual number only determined by the size of the crystal.

Question 23

In sodium chloride how many ions surround each corresponding ion?

Answer 23

a. Each Na+ ion is surrounded by 6 Cl- ions.

b. Each Cl- ion is surrounded by 6 Na+ ions.

Question 24

Within ionic compounds what are the similarities in melting and boiling points?

Answer 24

a. Almost all ionic compounds are solids at room temperature. At room temperature there is insufficient energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions in the giant ionic lattice. High temperatures are needed to provide the large quantity of energy needed to overcome the strong electrostatic force of attraction between ions. Therefore, most ionic compounds have high melting and boiling points.
b. The melting points are higher for lattices containing ions with greater ionic charges, as there is a stronger attraction between ions.

Question 25

Within ionic compounds what are the similarities in solubility?

Answer 25

a. Many ionic compounds dissolve in polar solvents, such as water. Polar water molecules break down the lattice and surround each ion in solution.
b. However, in a compound made of ions with large charges, the ionic attraction may be too strong for water to be able to break down the lattice structure. Therefore, the solubility decreases as the ionic charge increases.
c. However, predictions of solubility should be treated with caution as sometimes the ionic charges do not have the greater effect however in most scenarios this is the case.

Question 26

Within ionic compounds what are the similarities in conductivity?

Answer 26

a. In the solid state, an ionic compound does not conduct electricity. But once melted or dissolved in water, the ionic compound does conduct electricity
b. In the solid state, the ions are in a fixed position in the giant ionic lattice and there are no mobile charge carriers. As a result, an ionic compound is a non-conductor of electricity in the solid state.
c. When liquid or dissolved in water, the solid ionic lattice breaks down and the ions are now free to move as mobile charge carriers. As a result, an ionic compound is a conductor of electricity in liquid and aqueous states.

Question 27

What is covalent bonding?

Answer 27

Covalent bonding is the strong electrostatic force of attraction between a shared pair of electrons and the nuclei of the bonded atoms.

Question 28

In what direction does the bonding act in within a covalent bond?

Answer 28

The attraction in covalent bonding is localised, acting solely between the shared pair of electrons and the nuclei of the two bonded atoms.

Question 29

What is a double and a triple bond?

Answer 29

a. In a double bond, the electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonding atoms.
b. In a triple bond, the electrostatic attraction is between three shared pairs of electrons and the nuclei of the bonding atoms.

Question 30

What is a dative covalent or coordinate bond?

Answer 30

A dative covalent or coordinate bond is a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only. In a dative covalent bond, the shared electron pair was originally a lone pair of electrons on one of the bonded atoms.

Question 31

What is the average bond enthalpy?

Answer 31

Average bond enthalpy serves as a measurement of covalent bond strength. The larger the value of the average bond enthalpy, the stronger the covalent bond.