The periodic table Flashcards
What characteristics are seen down the periodic table?
Increasing radius, higher energy orbitals, increasing shielding and decreasing ionisation energy.
What characteristics are seen across the periodic table?
Increasing nuclear charge, similar radius, increasing ionisation energy.
What characteristics are seen diagonally down the periodic table?
Increasing ionisation energy and electronegativity.
How does the melting point of elements change down the periodic table?
Decrease down group one, increase down group seven, increase across a period up to group four and then drop sharply as elements form diatomic molecules held by weak intermolecular forces.
What are redox reactions?
Processes where both reduction and oxidation occur.
What is the difference between oxidation and reduction?
A species is oxidised if it loses electrons and reduced if it gains them.
What is the difference between an oxidising and reducing agent?
A reducing agent gives and electron to another species and is oxidised. An oxidising agent removes an electron from another species and is reduced.
Describe the group one elements reactions with water
Lithium- floats, fizzes and dissolves
Sodium- floats, fizzes, whizzes and dissolves
Potassium- floats, fizzes, explodes lilac flames
What are the flame colours?
Barium- apple green
Calcium- brick red
Potassium- lilac
Sodium- yellow
Lithium- red
What are the halogen precipitate colours?
Chloride- white precipitate
Bromide- cream precipitate
Iodide- yellow precipitate
Describe the appearance of the halogens
Fluorine- pale yellow gas
Chlorine- pale green gas
Bromine- brown liquid
Iodine- grey black solid
What is the general trend with group one elements?
Reactivity increases down the group and elements are more reactive than the group two elements, all soluble.
What is the general trend with group two elements?
Solubility increases down the group.
What is an electronegative element?
One having a strong affinity for an electron and thus acting as an oxidising agent.
What is the general trend with group seven elements (halogens)?
Melting points increase down the group, volatility decreases down the group, reactivity decreases down the group.
How is chlorine used in water treatment?
Water is treated with chlorine gas to make it safe to drink by killing typhoid and cholera bacteria.
How is fluorine used in water treatment?
Fluorine is added to toothpaste and sometimes water to prevent tooth decay and strengthen bones to reduce osteoporosis.
State a basic oxide
MgO or CaO.
State an acidic oxide
SO2 or NO2.
Where on the periodic table are basic oxides found?
The left hand side, with the bottom of the s block being most basic.
Where on the periodic table are acidic oxides found?
The right hand side, especially the upper parts of groups 5 and 6.
Why does ionisation energy increase across a group?
As there is a steady increase in the number of protons in the nucleus while the electron is in the same orbital and electron shielding isn’t increased much.
Why does ionisation energy decrease down a period?
As the outer electron is further from the nucleus due to more shells so the effective nuclear charge decreases.
What is meant by a displacement reaction in the halogens?
Reactions in which one halogen exchanges places with another halogen in a halide.
Why do displacement reactions occur with halogens?
Halogens higher in the periodic table are stronger oxidising agents and thus remove an electron from the halide to liberate the free halogen while being reduced to the halide.
Give the colours of the precipitates formed when sodium hydroxide is added to solutions containing metal ions
Mg2+ -white precipitate
Fe2+ -dark green precipitate
Cr3+ - grey green precipitate
Pb2+ - white precipitate
Describe halogens reacting with iron
Iodine- Strong heating required, slow reaction with brown residue.
Bromine- Little heat needed, quick reaction with dark vapours.
Chlorine- Violent reaction, iron ignites pale green vapours.
Why is chlorine the strongest oxidising agent?
It has the smallest radius with the nucleus closest to the outer shell, so it has the strongest attraction to electrons.
What are the solubility trends for sulphates?
Mg- soluble
Ca- insoluble (cloudy ppt)
Sr- insoluble (lighter ppt)
Ba- insoluble (heavy ppt)
What are the solubility trends for hydroxides?
Mg- insoluble
Ca- less insoluble
Sr- lesser insoluble
Ba- soluble
What are the solubility trends for carbonates?
All insoluble.
What is the test for sulphates?
Hydrochloric acid then Barium chloride, observation will be a white precipitate.
How to identify carbonates?
Add acids to carbonate, bubbles of CO2 should be produced (CASWC).
