Periodicity Flashcards
What ties together the different periods
Repeating trends in physical and chemical properties
What tied the different groups together
Similar chemical properties
Definition of first ionisation energy
Equation
The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous singly positively charged ions
X(g)———> X+ + e-
Definition of second ionisation energy and equation
The energy required to remove one electron from each ION of one mole of gaseous single positively charged ions to form one mole of gaseous doubly positively charged ions
X+(g)——> X2+(g) + e-
Explain the general shape of the graph of successive ionisation energies
Number of protons in the nucleus remains constant therefore as each electron is removed the remaining electrons should experience a linear increase in attraction
Why is the first ionisation energy the lowest
The electron is the furthest from the nucleus and experience the most shielding therefore it has the weakest attraction to the nucleus so takes the least amount of energy to remove
In a successive ionisation graph what does the jumps mean
The next energy shell has been moved to which is significantly closer to the nucleus and experiences less shielding so there is a greater attraction to the nucleus and more energy is required to move the electron
How can you tell an element from successive ionisation energy graph
Count the number of crosses before the first jump this is the group number and the total number of the crosses is the atomic number
What does the first ionisation energies of successive elements provide evidence for
Sub shells
Describe the GENERAL increase in the first ionisation energy across the second period
Going across each element has ONE EXTRA ELECTRON and ONE EXTRA PROTON
electron being added to the SAME ENERGY SHELLS
SAME degree of SHIELDING
GREATER ATTRACTION due to increases in nuclear charge = DECREASE in atomic RADIUS
More energy needed to remove them
Explain the trend in first ionisation energy across period 2
(Li-Be)
Increase
In both Highest energy electron in the 2S orbital but in Be there is an extra proton in the nucleus which leads to an increase in nuclear charge, a decrease in atomic radius and greater attraction for the electron so more energy required to move Be first electron
Explain the trend in first ionisation energy Be-B
Jump down lower then Be but not as low as Li
Despite the increase in nuclear charge and the corresponding decrease in the atomic radius which leads to greater attraction for the electrons
B is in the 2P sub shell compared to the 2S subshell in Be. The 2p electron is further from the nucleus than the 2s electron resulting in an overall weaker attraction so less energy required to remove it
Explain the trend in first ionisation energy B-N
Increase
In all of them the highest energy electron are all in separate orbitals in the 2p subshell. The addition of the proton leads to an increase in nuclear charge p, a decrease in atomic radius and greater attraction for the electrons so more energy required
Explain the trend in first ionisation energy N-O
Jump down not as low as C
Despite increase in nuclear charge and decrease in atomic radius which leads to greater attraction. A fourth electron is added to the 2p sub shell meaning one of the 2p orbitals contain a pair of electrons which leads to repulsion between said electrons decreasing amount of energy required to remove the electron
Explain the trend in first ionisation energy O-Ne
Increase
Highest energy electron all in 2p subshell
There is an increase in nuclear charge, decrease in atomic radius and greater attraction of electrons so more energy required to remove the electron
What do you add to the explanation for period 3 first ionisation trends
3s and 3p orbitals
What is the trend in first ionisation energies going down a group
Decreases
Despite increase in nuclear charge the highest energy electron is further away from the nucleus and more shielded which leads to a weaker electrostatic attraction so less energy required
Trend same for every group
Description of giant metallic structure
Continuous giant 3D regular arrangement of metal cations in a sea of delocalised outer shell electrons
Properties of a giant metallic structure
Conducts electricity- delocalised electrons can move through the solid and carry electrical charge
High MP + Bp- lots of electrostatic attractions between metal cations and delocalised electrons
Insoluble- attractions between the particles in the metal structure are stronger then the attractions to water molecules
Description of a giant covalent structure
Giant 3D regular arrangement of atoms held together by a network of covalent bonds that extend throughout the structure
Properties of a giant covalent structure
Doesn’t conduct electricity- no free moving charged ions or delocalised electrons
High Mp + Bp- lots of strong covalant bonds through the structure = hard to break
Insoluble in water- no significant attraction between the atoms of the substance and the water molecules. More energy required to break up with the covalent lattice than released from attractions with the water moleucles
Description of a simple molecular structure
Individual molecules containing atoms held together by string covalent bonds with weak intermolecular forces between molecules
Properties of simple molecular
Doesn’t conduct- no free moving charged ions or delocalised electrons
Low Mp+Bp- weak intermolecular forces between molecules
Varying in solubility- if imfs are similar in both solute and solvent then it’s more likely to be soluble
Description of atomic structure
Individual atoms with weak London forces between the atoms
