higher chemistry unit 1

monotomic gases

• stable

• low mp/bp

• He, Ne

• weak intermolecular forces (LDFs)

• single atom only

metallic lattice

• formed by metal atoms packed closely together

• held by delocalized electrons

• allows metals to conduct electricity and heat

• high mp/bp

covalent molecular

• solids -P_4, S_8, C_{(fullerene)(60)}

• gases - H_2, O₂, N₂, Cl₂

• Low mp/bp

covalent network

• B, C, Si

• C- Diamond

  - graphite →conducts electricity

• very high mp/bp

• strong covalent bonds are broken

electronegativity

the measure of attraction an atom in the bond has for the electrons in the bond

Across a period, electronegativity…

increases as there are more protons so theres an increased nuclear charge.

Down a group, electronegativity…

decreases as there are no other electron shells so theres an increased shielding effect.

Across a period, atomic size…

decreases as there are more protons so theres an increased nuclear charge

Down a group, atomic size…

increase as there are more electron shells so theres an increased nuclear charge.

first ionization energy

energy needed to remove one mole of electrons

second ionization energy

energy needed to remove more electrons from one mole of gaseous atoms

Across a period, ionization energy…

increases as there are more protons so theres an increased nuclear charge

Down a group, ionization energy…

decreases as there are more electron shells so theres an increased shielding effect

Equations for sodium

1st IE= Na→ Na⁺+e^-

2nd IE= Na⁺→ Na²⁺+e^-

3rd IE= Na²⁺→ Na³⁺+e^-

4th IE= Na³⁺→ Na⁴⁺+e^-

ionic bonding

• metal and non metal

• structure- ionic lattice

• high mp/bp

• conducts in solution

• not sold form

polar covalent

• uneven share of electrons in the bond

• different EN values

• resulting in positive and negative charges.

non polar covalent

• equal share of electrons in the bond

• same EN values

• resulting in no charges.

LDFs

• weakest intermolecular force

• experienced with all atoms and molecules

• uneven distribution of electrons

• force of attraction between a temporarily dipole and an induced dipole

PD-PDi’s

• intermolecular forces that occur between polar molecules.

• force of attraction between oppositely charged of neighboring polar molecules

hydrogen bonding

• arises when theres a high electronegativity difference, H bonded to N,O,F.

• strongest intermolecular forces

mp

solid → liquid

bp

liquid→gases

solubility

how easy a substance dissolves in a solvent

viscosity

how thick a substance is

intermolecular force that is the less viscous

LDFs

intermolecular force that is the most viscous

hydrogen bonds

more viscous as…

• there is a greater degree of hydrogen bonding so theres more hydroxyl groups

• stronger hydrogen bonds

splitting up redox

hints

• pick out species which are similar

• ignore balancing if it cancels out or simplifies

• copy exactly from data booklet

splitting up redox example

K+Pb²⁺→K⁺+Pb

K→K⁺+e^- oxidation

Pb²⁺+2e^- →Pb reduction

splitting up a redox with spectator ions

1. recognize the charge on the ions

2. cancel out spectator ions

3. ignore balancing if it cancels out

splitting up a redox with spectator ions example

oxidising agent

substance that accepts electrons

reducing agent

substance that donates electrons

oxidising and reducing agents example

writing more complex redox: identifying oxi/red agents

1. write all reactant species

2. remove spectator

3. write oxi & red equations

4. identify oxi & red agents

writing more complex redox: identifying oxi/red agents- example

writing complex ion-electron equations

1. balance the central atom (non oxygen) by adding a number in front of this atom

2. balance oxygen molecules by adding water molecules

3. balance hydrogen by adding hydrogen ions

4. balance the charge by adding electrons

writing complex ion-electron equations- example

standard solution

a solution of accurately known concentrations

preparing standard solution

1. dissolve sample in a small volume of distilled water

2. transfer multiple rinsing into a volumetric flask

3. fill flaskwith distilled water to the graduation mark.

titration calculation example

standard solution diagram