Module 2: Electrons and Bonding (Chapter 5)

Question 1

How do electrons orbit the nucleus?

Answer 1

In energy levels

Question 2

In the first 4 energy levels (shells) how many electrons are in each?

Answer 2

1 = 2 
2 = 8
3 = 18
4 = 32

Question 3

What is a shell?

Answer 3

A set of orbitals with the same quantum number (within the same energy level).

Question 4

Define an atomic orbital

Answer 4

A region within an atom that can hold up to 2 electrons with opposite spin.

Question 5

What are the 4 types of sub-shell?

Answer 5

s-, p-, d-, f-

Question 6

How many orbitals in each sub-shell?

Answer 6

n=1 has 1 orbital
n=2 has 4 orbitals
n=3 has 9 orbitals
n=4 has 16 orbitals

Question 7

Describe the s-orbital

Answer 7

Electron cloud is spherical
Can hold max of 2 electrons
Each energy level (shell) has 1 s-orbital
Greater the shell number, the larger the radius of the s-orbital

Question 8

Describe the p-orbital

Answer 8

Shaped like a dumb-bell
Found from n=2 upwards
Each shell contains 3 p-orbitals (3x2e-)
Arranged at right angles to each other in Px, Py and Pz

Question 9

Describe the d-orbital

Answer 9

Each shell from n=3 upwards contains 5 d-orbitals (10e-)

Question 10

Describe the f-orbitals

Answer 10

From n=4 upwards.

Each shell contains 7 f-orbitals (14e-)

Question 11

How are electrons represented in a box?

Answer 11

Half-headed arrows. Always fill in singularly first.

Question 12

How can shorthand electronic configuration be written?

Answer 12

Use of noble gases in square brackets with remaining outer electron sub-shells.

Question 13

What is an ion?

Answer 13

Electrically charged particle formed from the lose or gain of electrons.

Question 14

What happens to configuration when a positive ion forms?

Answer 14

Electrons are removed from the highest energy orbitals (further from the nucleus).

Question 15

What happens to configuration when a negative ion forms?

Answer 15

Electrons are added to the highest energy orbitals.

Question 16

What is different about d-block elements when forming ions?

Answer 16

The 4s-sub-shell is filled before the 3d-sub-shell. This means the reverse is true when making ions. The 4s-sub-shell electrons are lost before the 3d-sub-shell electrons.

Question 17

Why are the noble gases so unreactive?

Answer 17

The s and p sub-shells are full. All the electrons are paired to another electron of opposite charge. They fulfil the Octet rule.

Question 18

What are other atoms trying to acheive?

Answer 18

Obtain the Octet rule. A noble gas electron configuration, by bonding with other elements - sharing or transferring electrons in chemical bonds.

Question 19

Define ionic bonding

Answer 19

Electrostatic attraction between a metal and non-metal, formed from the transfer of electrons, to form a giant ionic lattice structure.

Question 20

Why do ionic compounds have a high mpt and bpt?

Answer 20

Strong electrostatic forces of attraction between oppositely charged ions, requiring a lot of energy to overcome. Hence high mpt and bpt.

Question 21

Are ionic compounds soluble?

Answer 21

Soluble in polar solvents like water. Break down the lattice and surround each ion in solution. Partial charge of water causes the anion to be attracted to hydrogen and cation to oxygen. Compounds with larger charges will not be able to be broken down by water, as attraction is too strong.

Question 22

Do ionic compounds conduct electricity?

Answer 22

In a solid state no, but when molten or aqueous, the ions in the solution are mobile, so are mobile charge carriers. When solid the ions are fixed in position, and are not mobile charge carriers.

Question 23

What structure do ionic bonds form?

Answer 23

Giant ionic lattice

Question 24

What are the general rules for different groups, when forming ionic compounds?

Answer 24

Groups 1-3 lose electron to form cations
Group 4 don’t form ions as too much energy is required
Groups 5-7 gain electrons to form anions
Group 0 do not form ions as they are Nobel gases

Question 25

Define covalent bonding

Answer 25

Electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms. There is overlap of the atomic orbitals, where the electrons are shared.

Question 26

What is the type of attraction in a covalent bond?

Answer 26

Attraction is localised between the nuclei of the two bonding atoms. This an result in a molecule forming.

Question 27

What are lone pair?

Answer 27

Electrons in the outer shell not used in bonding. A concentrated region of negative charge around the atom. Can influence the shape and chemistry of the molecules.

Question 28

Why are there exceptions to the Octet rule?

Answer 28

The Octet rule is not always possible to achieve. May not be enough electrons to react an octet. More than 4 pairs of electrons can form in the bonding. Boron is an example of where only 3 pair of electrons can form due to only having 3 outer electrons.

Question 29

Why are elements in groups 5-7 of period 3 exceptions to the Octet rule?

Answer 29

The n=3 shell can hold 18 electrons. The is me and that more electron are available for bonding, so expansion of the Octet occurs.

Question 30

What are the general rules for the exceptions to the Octet?

Answer 30

Non-metals in group 5 can form 3-5 covalent bonds. Non-metals in group 6 can form 2, 4 or 6 covalent bonds. Non-metals in group 7 can form 1, 3, 5 or 7 cb.

Question 31

What happens in a double bond?

Answer 31

The electrostatic attraction is between 2 shared pair of electrons and the nuclei of the bonding atoms. E.g CO2

Question 32

What is a triple covalent bond?

Answer 32

The electrostatic attraction is between 3 shared pairs of electrons and the nuclei of the bonding atoms.

Question 33

What is a dative bond?

Answer 33

Known as a coordinate bond, this is when a shared pair of electrons has been provided by one of the bonding atoms only.

Question 34

What are some of the proportions of simple covalent molecules?

Answer 34

Weak intermolecular forces between molecules - low energy to separate the molecules - low melting and boiling points. Do not conduct electricity - no charged particles available. Non-soluble in polar solvents, but soluble in polar solvents. E.g. hexane. This is due to London forces between the solvent and the molecule.

Question 35

Describe some of the properties of giant covalent structures

Answer 35

Joined by strong covalent bonds, meaning high melting and boiling points. Not soluble in either polar or non-polar solvents. The covalent bonds are too strong to the broken. Strength of covalent bonds are measured by ‘average bond enthalpy’. Form a giant lattice structure. Graphite is the only one which can conduct, due to the mobile delocalised electron. Silicon dioxide is an example, where their is a tetrahedral structure, and is joined to 4 oxygen atoms.