The Periodic Table Flashcards
Define a group of the periodic table
A vertical column in the periodic table. Elements in a group have similar chemical properties. And their atoms have the same number of electrons in their outer shell.
Define a period of the periodic table
A horizontal row in the periodic table. Elements show trends in properties across a period.
What is periodicity
The regular repeating pattern in properties of the elements across different periods.
How is a subshell different to an orbital
A sub shell is a group of the same type of orbitals e.g p-orbitals
Orbitals are regions within an atoms that contain up o 2 electrons.
Explain why the 1st ionisation energy decreases between Be and B
- Between groups 2 and 3 the p subshell begins to fill.
- In Be the outer electron is in the 2s orbital.
- In B the outer electron is in a 2p orbital
- The 2p orbital in B is of higher energy and experiences more shielding from inner electrons.
- Despite the fact that the nuclear charge increases by +1 from Be to B,
- The difference in shielding and energy means the nuclear attraction is weaker in B, so less energy is required to remove it’s outer electron.
Why do group 4 elements have the highest melting points fro periods 2 and 3
Because carbon and silicon form giant covalent structure - bonding to 4 other atoms- this requires a lot of energy to break. Boron only has 3 covalent bonds so has a lower melting points.
Describe the trend in atomic radii across a period
- The atomic radius decreases
- As you go across a period there is a very little increase in electrons shielding
- However there is a regular increase in nuclear charge +1
- The overall effect is that the outer electrons are pulled more strongly towards the nucleus as you go across a period.
Write reactions of group 2 metals with oxygen, water and acid
Metal (s) + Oxygen (g) –> Metal Oxide (s)
Metal (s) + Water (l) –> Metal Hydroxide (aq) + Hydrogen (g)
Metal (s) + Acid (aq) –> Salt (aq) + Hydrogen (g)
Write electron half equations for the reaction of group 2 metal and Oxygen
M –> M2+ + 2e-
O + 2e- –> O2-
Write balanced symbol equations for barium with ethanoic acid
Ba (s) +2CH3COOH (aq) –> Ba(CH2COO)2 (aq) + H2 (g)
What figures should you look at when linking ionisation energy and reactivity with water in group 2 metals
The sum of the 1st and 2nd ionisation energies
Group 2 metals form 2+ ions so two electrons must be removed. The energy required to do this is the sum of the 1st and 2nd IE.
Suggest why ionisation energy will not be the only factor that affects reactivity of the metal towards water
IE suggests the metal is a gas which isn’t the natural states of a lot of metals.
Describe the trend in reactivity as you go down group 2
The reactivity increases as you go down the group as IE decreases.
Write equation of a group 2 metal oxide with water.
And write observations
MO (s) + H2O (l) –> M(OH)2 (aq)
First the metal oxide would dissolve and then a cloudy white solution would form.
Define solubility
A measure of the ability of a solute to dissolve in a solvent. (moldm-3)
Define alkali
A type of base that dissolves in water forming hydroxide ions.
Define alkaline
A term used to describe a solution containing hyroxide ions.
Define alkalinity
A measure of the concentration of hydroxide ions present in an alkaline solution (moldm-3)
Define pH
A measure of the concentration of hydrogen ions present in a solution.
Describe increase in pH of group 2 metal hydroxides as you go down the group.
As you go down the group the solubility of the metal hydroxides increases.
This means there will be more OH- ions in the solution.
This makes it more alkaline so increases the pH.
Describe chlorine- state, colour and hazards at R.T
Gas, Green and Toxic
Describe bromine- state, colour and hazards at R.T
Liquid, brown (orange vapour), toxic and corrosive
Describe iodine- state, colour and hazards at R.T
Solid, grey, toxic vapour formed when heated
What is trend in boiling point as you go down group 7
Boiling point increases so reactivity decreases
What affects the boiling points of halogens
London forces- so number of electrons
In which halogen molecule, Cl2, Br2 or I2, is the covalent bond strongest and why
Cl2
Because the covalent bond is formed by a pair of electrons between the atoms attracting the nuclei of these atoms. The close the electrons are to the nucleus the stronger the attraction.
Write colours of chlorine, bromine and iodine in water and in cyclohexane
Chlorine 1. water- very pale green (colourless) 2. cyclohexane- pale green (colourless) Bromine 1. water- orange 2. cyclohexane- orange Iodine 1. water- brown 2. cyclohexane- violet
What is the colours of the halogen ions
colourless
Why do two layers from when an organic solvent is added to a solution containing halogens
- Because the two layers are immiscible
- Hexane is non-polar - only forms London forces between molecules
- But water forms hydrogen bonds
Write chemical equation for reaction between chlorine solution and potassium bromide
Cl2(aq) + 2KBr(aq) –> Br2(aq) + 2KCl(aq)
Which layer of the 2 layers formed when an organic solvent to halogens is organic
The top layer- it is less dense
Define disproportionation
The oxidation and reduction of the same element in a redox reaction
Write equation for the reaction of chlorine with water
Chlorine + water –> chloric (I) acid + hydrochloric acid
Cl2(g) + H2O(l) –> HClO(aq) + HCl(aq)
Why is chlorine added to drinking water
To kill bacteria
What affects the reactivity of halogens
The decreasing ease of forming 1- ions - IE energy
What are risks of adding chlorine to water
Chlorine can react with hydrocarbons producing products which are suspected carcinogens
Write reaction of Chlorine with sodium hydroxide
Chlorine + sodium hydroxide –> sodium chlorate (I) + sodium chloride + water
Cl2(g) + 2NaOH(aq) → NaClO(aq) + NaCl (aq) + H2O(l)
Why is sodium chlorate (I) more effective as a bleach than chloric (I) acid
It doesn’t decompose as readily so lasts longer
What happens to the pH of group 2 metal hydorxides as you go down the group
It increases Mg- 10 Ca- 11 Sr- 12 Ba- 13
Describe the trend in solubility of the group 2 metal hydroxides as you go down the group
The solubility increases
How is the solubility of the metal hydroxides related to the alkalinity
More soluble means more oh- ions present so more alkaline
What is the most common type of reaction with a group 2 metal
Redox reaction:
Each metal atom is oxidised losing 2 electrons
Show redox reaction with Mg and oxygen
2Mg(s) + O2 (g) → 2MgO (s)
- Each Mg loses two electrons - oxidised
- Each O gains two electrons - reduced
Show redox reaction with Sr and water
Sr (s) + 2H2O (l) →Sr(OH)2 (aq) + H2 (g)
- Each Sr loses two electrons- oxidised
- Two of the H decrease by 1 oxidation number forming H2
- Two H don’t change forming Sr(OH)2
Show redox reaction woth HCl and Mg
Mg (s) + 2HCl (aq) →MgCl2 (aq) + H2 (g)
- Each Mg loses two electrons - oxidised
- Each H decreases oxidaiton number by 1- reduced
Give an example of how group 2 compounds can be used in agriculture
- They are basic so can neutralise acids
- Calcium hydroxide is added to fields
- It neutralise acid in soil to form water
Ca(OH)2 (s) + 2H+ (aq) → Ca2+ (aq) + 2H2O (l)
Give an example of how group 2 compounds can be used in medicine
- They are used as antacid for treating acid indigestion
- They neutralise the acid in your stomach- CaCO3 (s) and Mg(OH)2 (s)
Mg(OH)2 (s) + 2HCl (aq) → MgCl2 (aq) + 2H2O(l)
CaCO3 (s) +2HCl → CaCl2 (aq) + H2O (l) + CO2 (g)
