Periodicity Flashcards
What is the first ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
What is the first ionisation of Mg?
Mg(g) ——> Mg+ (g) + e-
What is the second ionisation of Mg?
Mg+(g) ——> Mg2+ (g) + e-
What is shielding?
When inner electrons screen the outer electrons from the pull from the nucleus
What is nuclear charge?
The positive charge on the nucleus
What is atomic radius?
Radius of an atom. We measure atomic radius by measuring the distance between two nuclei of touching atoms and halving the distance
What happens to the shielding across period 3?
Stays the same
What happens to the nuclear charge across period 3?
Increases
What does a stronger nuclear charge mean?
The closer the electrons are pulled to the nucleus
What happens to the atomic radius across period 3 and why?
Decreases as electrons pulled closer to nucleus
What is the general trend of first ionisation energy across period 3?
Increases
Why does the first ionisation energy increase across period 3?
Nuclear charge increases
Attraction of electrons increase
Atomic radius decreases
Takes more energy to remove 1st e-
Why is there a dip in the trend between Mg and Al in period 3?
Mg has full sub shell stability (3s)
Al has one electron in higher sub shell
So easier to remove as further from nucleus
Al= lower 1st IE
Why is there a dip in the trend between P and S in period 3?
P has half sub shell stability (3p) S has 3p containing a pair of electrons Pair of electrons repel each other So one of these electrons easier to remove S= lower 1st IE
What is the general trend of 1st IE down group 2?
Decreases
Why does the first ionisation energy decrease down group 2?
More inner shell electrons as you go down group
So shielding increases
Atomic radius increases so electrons further away
Nuclear attraction decreases
So easy to remove first electron
How do you draw metal diagram?
At least 6 cations
Sea of delocalised electrons
Cations in fixed position
Each cation has a positive charge
What are the properties of metals?
Electrical conductivity High melting + boiling point Solubility Good thermal conductor Malleable
Why do metals conduct in solid and liquid?
Because delocalised electrons can move freely within the lattice
Why do metals have high melting + boiling point?
Strong electrostatic attraction between metal ion + delocalised electron
So needs lots of energy to break
Do metals dissolve in solvents?
NO
Why are metals good thermal conductors?
Because when heated e- gain KE so move faster
Movement transfers gained energy throughout metal
Why are metals malleable?
Because no bonding between ions therefore layers can slide
What are alloys?
Mixture of two or more metals
What do alloys do?
They dissort the layers so they can’t slide therefore making the metal harder
What are the giant covalent structures?
Diamond
Graphite
Fullerenes
Graphene
What is the structure of diamond?
Giant covalent
Lattice
Made of carbon
Each carbon is bonded to 4 other carbons
What are the properties of diamond?
Hard - giant covalent structure + lots of strong bonds
Doesn’t conduct - no e-
High melting point - strong covalent bonds = needs lots of energy to break
What is the structure of graphite?
Made of carbon Hexagonal structure Strong covalent bonds Parallel layers Weak intermolecular forces between layers Each carbon bonded to 3 carbons e-
What are the properties of graphite?
Soft/slippery - layers slide as weak forces between
Conduct - e-
High melting point
Why does graphite have a high melting point?
Giant structure with lots of strong covalent bonds between atoms so need lots of energy to break bonds
What are fullerenes?
Cage like structures
What are examples of fullerenes?
Nanotubes
Buckminster fullerenes
What is an allotrope?
Different physical forms of an element
What is the structure of graphene?
One layer of graphite
Sheet of carbons joined together in hexagons
One atom thick = 2D compound
What are the properties of graphene?
Conducts - e-
Strong - delocalised electrons strengthen covalent bonds
Transparent + light - single layer
What is graphene used in?
Touchscreens
High-speed electronics
Aircraft technology
What is the general trend of melting point across period 3?
Increases to Si then decreases afterwards
Why does the melting point increase (across period 3) from Na to Al?
Charge on metal ion increases
So no. of e- increases
So strength increases
So more energy needed to break bonds
Why does Si have the highest melting point in period 3?
Have to break lots of covalent bonds
Requires lots of energy
Giant covalent structure
Why does the melting point (after Si) decrease across period 3?
Non-metals
So exist as simple molecules with weak London forces between molecules
So need little energy to break
Why does S have an elevated melting point in comparison to the other non-metals in period 3?
Has more electrons since it has more molecules
As exists as S8
So more London forces
So more energy needed to break bonds
What does P exist as?
P4
What does S exist as?
S8
What does Cl exist as?
Cl2
What does Ar exist as?
Ar since it is monoatomic
Why is diamond a poor electrical conductor?
Outer electrons are in localised covalent bonds
Why is graphene a better conductor than graphite?
No layers to slow down electrons
From a successive ionisation energies graph how can you work out which group it is from?
Count how many electrons are removed before the first big jump
From a successive ionisation energies graph how can you work out the electronic structure of the element?
Working from right to left count how many points there are before each jump to find out how many electrons there is in each shell
