5 Electrons and Bonding Flashcards
How many electrons are in the first four shells?
n1 = 2
n2 = 8
n3 = 18
n4 = 32
What is a shell?
Shells are regarded as energy levels
The energy increases as the shell number increases
The shell number is called the principle quantum number
What is an atomic orbital?
A region around the nucleus that can hold up to two electrons, with opposite spin
What are the different types of orbitals?
S, p, d and f orbitals
Describe the shape of the s and p orbitals
S: the electron cloud is within the shape of a sphere
P: The electron cloud is within the shape of a dumb-bell
How many orbitals are in each shell (n1, n2, n3, n4)? How many electrons are in each orbital?
n1 = 1 s-orbital –> 2
n2 = 3 p-orbitals –> 6
n3 = 5 d-orbitals –> 10
n4 = 7 f-orbitals –> 14
How many electrons can an orbital hold?
Two electrons
How do the orbitals fill?
Order of increasing energy
What is the order of filling orbitals?
1s, 2s, 2p, 3s, 3p, 4s, 3d
Why does 4s sub-shell fill before 3d sub shell?
3d sub shell is at a higher energy than the 4s sub shell (therefore 4s fills before 3d as orbitals fill in order of increasing energy)
How and why do you draw electrons in the ‘electrons-in-box’ model?
Electrons are negatively charged and repel one another
Electrons have a property called spin - either up or down (shown as an arrow)
Two electrons in an orbital must have opposite spins to counteract the repulsion between the negative charges of the two electrons
How are orbitals filled?
For orbital with the same energy, the electrons occupy each orbital singly first in order to minimise repulsion between paired electrons
How do ions form regarding electron configuration?
The highest energy sub-shells lose or gain electrons
What happens with the 4s shells with ions?
4s sub-shell fills before the 3d sub-shell
4s sub-shell also empties before the 3d sub-shell
Define ionic bonding
The electrostatic attraction between positive and negative ions
Why does a giant ionic lattice structure form?
Each ion attracts oppositely charged ions in all directions
What state are ionic compounds in at room temperature and why?
- Almost all solids at room temperature
- At RT there is insufficient energy to overcome the strong. electrostatic forces of attraction between the oppositely charged ions in the giant ionic lattice
Why do ionic compounds have high melting and boiling points?
High temperatures are needed to provide the large quantity of energy needed to overcome the strong electrostatic attraction between the ionic
In which cases are melting points higher for certain ionic compounds?
Lattices with ions with greater ionic charges, as there is stronger attraction between ions
Ionic attraction also depends on the size of the ions
Describe the patterns of ionic compounds solubility
-Many ionic compounds dissolve in polar solvents e.g. water
-Polar water molecules break down the lattice and surround each ion in solution
-If a compounds is made of ions with large charges, the ionic attraction may be too strong for water to break down the lattice
What are the two main processes solubility requires?
-Ionic lattice must be broken down
-Water molecules must attract and surround the ions
Solubility depends of relative strengths of the attractions within the giant ionic lattice and the attraction between ions and water molecules
Do ionic compounds conduct electricity as solid and why?
No
The ions are in a fixed position in the giant ionic lattice
There are no mobile charge carriers
Non-conductor
Do ionic compounds conduct electricity as a liquid or dissolved in water?
Yes
Solid ionic lattice breaks down
Ions are now free to move as mobile charge carriers
Define covalent bonding
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What is the orbital overlap in a covalent bond?
A covalent bond is formed by the overlap of atomic orbitals, each of which contains 1 electron to give a shared pair of electrons
What are the 2 main points about the covalent bond itself?
The shared pair of electrons is attracted to the nuclei of both the bonding atoms
The bonded atoms often have outer shells with the same electron structure as the nearest noble gas
What is the difference between ionic and covalent interactions?
The attractions in a covalent bond is very localised and hence we can get molecules
What is a lone pair?
Paired electrons that are not shared
What is a dative bond?
A covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only - originally a lone pair
What is the average bond enthalpy?
A measurement of covalent bond strength (larger the value of the average bond enthalpy the stronger the covalent bond)
