What type of compound is sodium chloride
Ionic compound
Properties of ionic compounds
1)Conduct electricity when molten or in a solutuion.
2) High melting point and Boiling ppoint
3) Hard
4) Brittle
5) Crystal structures
Explain why potassium has a lower melting point than calcium?
Calcium donates 2 electrons to the sea of delocalised electrons (1)
Calcium forms stronger metallic bonds(1)
So more energy is required to break the bonds.(1)
Why do ionic compounds conduct electricity when molten?
Ions are free to move(mobile)
Properties of metallic bonding
high melting points
malleability
ductility
Good electrical and thermal conductivity
Metallic luster (shiny surface due to light bouncing off it’s free electrons)
Properties of covalent bonding
Low melting/ Boiling points.
Poor electrical conductivity.
What is formed when metals burn in oxygen?
Metal bunt in oxygen is Oxidation reaction
Metal Oxide
Formula of Magnesium Oxide
MgO
Avogadro’s constant
6.02 × 10²³ per mole
What is a mole in chemistry?
A unit measuring the amount of a substance, measuring a large number of particles.
Group 1 is AKA
Alkali metals
What is meant by ionisation energy?
Energy required to remove 1 mole of electron from a gaseous atom.
1st ionisation energy of lithium
Li⁺(g) + e⁻. =520
1st ionisation energy of lithium
Li(g) +→Li(g) + e⁻ = 520KJ/mol
Explain why the first ionisation energy of the top 3 group 1 elements decrease as the atomic number increases (4)
There are more electronic shells as you move down the elements(1).
So, the outer electrons are further away from the nucleus. (1)
This creates less shielding between the nucleus and the electrons. (1)
Therefore, the nuclear attraction decreases more and more. (1)
What are London dispersion forces?
The weakest intermolecular attractions rising from temporary, instantaneous dipoles in neighbours leading to weak attractions.
Explain the difference in boiling points between water and methane, in terms of intermolecular forces present?
Water has a higher boiling point than methane, because water molecules form hydrogen bonds(1)
Which is the strongest intermolecular force(1)
This requires significant energy to break(1)
water is dipole-dipole forces. (1)
Whereas, methane molecules experience london dispersion forces(1)
which need very little energy to overcome for boiling.(1)
the polar nature of water due to oxygen’s high electronegativity creates these strong attractions unlike methane’s non-polar.
Define electronegativity
Ability of an atom to attract a pair of electron in a covalent bond towards itself
Explain why C-Cl bond is polar
Cl is more electronegative than C so Cl becomes delta negative and C is delta positive.(2)
There are Van der Waals forces between non-polar molecules,
Explain what causes these forces.
Random movement of electrons(1)
induces a dipole in another molecule(1)
These temporary dipoles in different molecules attract(1)
C-CI bond is polar, but C-Cl4 is a non-polar molecule.
Explain Why (2marks)l
It’s symmetrical and they cancel eachother out
Does Methane(CH4) or Carbon dioxide(CO2), have stronger bonds?
CO2: Contains strong carbon-oxygen double bonds, which are inherently strong, giving its bonds more s-character, making them very stable.CH4: Consists of four weaker carbon-hydrogen single bonds
How does a potassium atom form a potassium ion?
It loses 1 electroN
