CHAPTER 7: Periodicity Flashcards
Define PERIODICITY.
The repeating trend in properties of elements across each PERIOD.
What do elements in the same GROUP share?
Same number of electrons in highest outer energy level.
BLOCKS are divided according to the sub-shell with the highest energy.
So what block is Oxygen in? And Sodium?
Oxygen = p-block Sodium= s-block
What group are the HALOGENS?
group 17 (7)
What is ionisation energy a measure of?
a measure of how easily electrons are lost from an atom to form positive ions
Define FIRST IONISATION ENERGY.
the energy required to remove ONE electron from each atom in one mole of GASEOUS atoms of an element to form one mole of gaseous 1+ ions.
Define SECOND IONISATION ENERGY.
the energy required to remove ONE electron from each atom in one mole of GASEOUS atoms of an element to form one mole of gaseous 2+ ions.
Why is second ionisation energy greater than the first ionisation energy?
More energy is required to remove the next electron in the highest energy level because the nuclear attraction for that electron becomes stronger.
What are the 3 factors that affect ionisation energy?
- Atomic Radius: greater distance between nucleus and outer shell means less nuclear attraction.
- Electron shielding: electrons repel so more shielding leads to more repulsion so less nuclear attraction for outer electrons
How many ionisation energies does an element have?
SUCCESSIVE IONISATION
The same number of electrons that they have.
Give the first and second ionisation equation for hydrogen.
H(g) -> H+(g) + e- FIRST IONISATION ENERGY
H+(g) -> H2+(g) + e- SECOND IONISATION ENERGY
What should you remember about reading a successive ionisation energy graph of an element?
That the first few ionisation energies are for the OUTER shell, so you are counting the electrons from the OUTSIDE IN.
What 3 things can you predict from successive ionisation energies?
1) number of electrons in outer shell and therefore the GROUP
2) number of shells
3) the identity of the element
What does a large jump in ionisation energies of successive ionisation energies indicate?
A new, different shell
Why is there an increased jump when you reach a new shell?
The next shell is closer to the nucleus so a lot more energy is required to overcome the nuclear electrostatic attraction.
What is the trend of first ionisation energies DOWN A GROUP? why?
it decreases because less energy is required to overcome nuclear attraction.
- Atomic radius increases
- more shielding
What is the trend of first ionisation ACROSS A PERIOD?
a GENERAL increase.
but there are 2 falls.
Explain the 2 falls that occur across the trend of first ionisation energies of a period.
the first fall = removing an electron that is starting to fill a p-subshell. (a higher energy level than the previous s-subshell)
the second fall = removing the electron that is starting to pair with the electrons in an orbital. The repulsion leads to less energy required.
(see page 98)
Metals vary in properties but what common properties do all metals have?
- they all have the ability to CONDUCT ELECTRICITY.
- Strong metallic bonds
- High melting and boiling points
What is METALLIC BONDING?
BONDING FOR METALS:
- in a solid metal structure, each atom has donated its outer shell electrons to a pool of electrons that are delocalised throughout the structure.
- The positive ions (cations) and delocalised electrons form an electrostatic attraction.
The cations are FIXED. Only the delocalised electrons are able to move.
Why can metals conduct electricity?
The delocalised electrons act as MOBILE CHARGE CARRIERS and can carry the charge across the structure when voltage is applied.
Why do metals have high melting and boiling points?
Large amount of energy is required to overcome the strong electrostatic attraction between the cations and electrons (metallic bonds)
Are metals SOLUBLE?
no.
interactions with solvents are rather REACTIONS.
What are GIANT COVALENT LATTICES?
When MANY atoms are held together by numerous strong covalent bonds to give a 3D structure.
What are GIANT METALLIC LATTICES?
When MANY atoms are held together by metallic bonding to form a 3D lattice.
Why do GIANT COVALENT Lattices have HIGH melting and boiling points?
The covalent bonds are strong so lots of energy is required.
Are giant covalent lattices soluble?
No, the covalent bonds are too strong to be overcome by interaction with solvents.
Can giant lattice conduct electricity?
No.
EXCEPT graphite and graphene.
Why can Graphite and Graphene conduct electricity but diamond can’t?
In diamond, all electrons of carbon atom is being used in covalent bonds.
In graphite and graphene, the carbon atoms are arranged in PLANAR HEXAGONAL LAYERS with spare electrons delocalised within the layers. These act as mobile charge carries and carry charge across the lattice.
Describe the PERIODIC trend in melting points.
-General increase from group 1 to group 14 (4) as metals and giant covalent lattices have high melting points.
-Sharp decrease between giant molecular structures and the simple molecules as the forces are weak.
(page 103)
