3.1 key concepts Flashcards
In a periodic table where can you find s block elements?
Groups 1 and 2
In a periodic table where can you find p block elements?
From groups 3 to 8
In a periodic table where can you find d block elements?
In the area cluster with transition metals (the gap from group 2 and group 3)
In a periodic table where can you find f block elements? (NOT REQUIRED)
Actinides and Lanthanides
What is meant by periodicity?
Trend that occur (in physical and chemical properties) and you move across the periods of the periodic table
How are elements arranged in the periodic table?
Elements are arranged using increasing atomic number (number of protons) from LEFT to RIGHT
What is meant by atomic radius?
The distance of the outermost electron from the nucleus
What is the trend in atomic radius and why?
Atomic radius decreases across the period and increases down the group.
It decreases across the period because the electrons across the period are pulled closer together
It increases down the group because the electrons are in a different energy level. This is because as you have more electrons, more shells are needed
What is meant by electronegativity?
The ability of an atom to attract a pair of electrons in a covalent bond
What is the trend with electronegativity and why??
Electronegativity decreases down a group
Electronegativity increases across a period
As you go down, there are more shells, so there is more shielding meaning that it is harder for the atom to attract electrons
What is meant by melting point/boiling point?
A measure of the energy required to separate the particles in a substance
What is the trend with melting point/boiling point and why?
Metals - High melting point. Increases across the period due to the increasing number of metallic bonding between the positively charged metal ions (cations) and the delocalised electrons
Non-metals - High melting point as it has a giant molecular structure like diamond. A lot of energy is needed to break the covalent bonds holding the atoms together
Give a description of metallic bonding
- Sea of delocalised, free moving electrons
- Giant lattice of positive ions
- Strong electrostatic attractions between the positive ions and the delocalised electrons
What are the properties of metallic bonding?
1) High melting point. - Increases across the period due to the increasing number of metallic bonding between the positively charged metal ions (cations) and the delocalised electrons
2) Malleable - can be hammered into shape
3) Can conduct electricity due to the delocalised electrons
Describe the trend of metallic bonding ranging from group 1 to group 3
Group 1 - Weakest level of metallic bonding
Group 2 - In the middle
Group 3 - Strongest type of metallic bonding
NOTE: Just because it is the weakness type of metallic bonding, it doesn’t mean metallic bonding is weak. Metallic bonding is very strong, but it strength depends on the charge (+1,+2 or +3 ) of the ion formed
What is meant by covalent bonding?
The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
What are the properties of covalent bonding?
Low melting/boiling point due to the weak intermolecular forces between atoms that require little energy to break
Cannot conduct electricity as there are no delocalised electrons
Only soluble in NON-POLAR solvents (remember like dissolves like)
What is the trend with ionisation energy and why?
Ionisation energy decreases down the group
Ionisation energy increases across the period
Decreases down the group - This is because as we go down the group, atomic radius increases. This means that the outermost electron is further away from the the nucleus. This increase shielding (the repulsion of outer electrons by inner electrons) As shielding increases it means that the outermost electron is less attracted to the nucleus so it can be easily lost.
Increases across the period - This is because across the period both atomic radius and shielding decreases meaning that the outermost electron is now closer to the nucleus allowing it to form a strong attraction with it. This means it will now more energy for the element to ionised.
What does the value of ionisation energy depend on?
- Atomic radius
- Size of nuclear charge (How positive the atom or ion is)
- Shielding (the repulsion of outer shell electrons by inner shell electrons)
How do you represent ionisation energy?
M(g) → M+(g) + e-
NOTE : M = Metal (g) = Gaseous (Gas state)
e- = Electron M+ = Metal ion
Give the ionisation energy of Potassium (Group 1)
K(g) → K+(g) + e-
Give the ionisation energy of Magnesium (Group 2)
Mg+(g) → Mg2+(g) + e-
NOTE : Mg+ = Metal ion [first ionisation energy]
(g) = Gaseous (Gas state) e- = Electron
Mg2+ = Metal ion [second ionisation energy]
Give the ionisation energy of Aluminium (Group 3)
Al2+(g) → Al3+(g) + e-
NOTE : Al2+ = Metal ion [second ionisation energy]
(g) = Gaseous (Gas state) e- = Electron
Al3+ = Metal ion [third ionisation energy]
Are successive ionisation energies higher or lower than the previous one , and why?
Successive ionisation energies are always greater than the previous one
This is because the electron is being pulled away from a more positive species
Where there is a change in shell, what does it do to ionisation energy?
A charge in shell will lead to a LARGE increase in ionisation energy.
This can be used to predict the group of an unknown element
What is the trend for electronic configuration?
Number of electron shells increases down the group
In group 2, what properties increase down the group?
- Atomic radius
- Ionic radius
- Reactivity
In group 2, what properties decrease down the group?
- Melting Point
- Boiling point
- Ionisation energy
Why do group 7 elements react?
To get a full outer shell. To get this, they must gain an electron.
In group 7, what properties increase down the group?
- Atomic radius
- Ionic radius
- Melting point
- Boiling point
In group 7, what properties decrease down the group?
- Electronegativity
- Reactivity
- Ionisation energy
Describe the appearance of FLUORINE (colour in water, colour in cyclohexane and state at RTP)
Colour in water - Yellow
Colour in cyclohexane - Yellow
State at RTP - Gas
Describe the appearance of CHLORINE (colour in water, colour in cyclohexane and state at RTP)
Colour in water - Pale green
Colour in cyclohexane - Pale Green
State at RTP - Gas
Describe the appearance of BROMINE (colour in water, colour in cyclohexane and state at RTP)
Colour in water - Orange
Colour in cyclohexane - Orange
State at RTP - Liquid
Describe the appearance of IODINE (colour in water, colour in cyclohexane and state at RTP)
Colour in water - Brown
Colour in cyclohexane - Violet
State at RTP - Solid
What is a redox reaction?
A reaction where reduction and oxidation happens simultaneously (at the same time)
What is the oxidation number of elements?
0
NOTE - It is always ZERO and this value will NEVER change
e.g. Li - 0
Na - 0
Br2 = 0
What is the half equation for Magnesium?
Mg → Mg2+ +2e-
Mg = Magnesium e- = electron
What is the half equation for Oxygen?
O + 2e- → 02-
Does magnesium react quick or slow with COLD water? (Provide the equation aswell)
Magnesium reacts very SLOWLY with water
Mg (s) + 2H2O(l) → Mg(OH)2 (aq) + H2(g)
Does magnesium react quick or slow with STEAM? (Provide the equation aswell)
Magnesium reacts quickly with steam
Mg (s) + H2O(g) → MgO (s) + H2(g)
Describe the trend with group 2 metals and water
As you go down the group, reactions become more vigorous
Is this a redox reaction? How do you know?
Mg + H2O → MgO + H2
Mg gets oxidised from 0 to =2 and H gets reduced from +1 to 0
What is thermal decomposition?
Decomposition of a compound using heat
e.g. MgCO3 (s) + HEAT → MgO (s) + CO2 (g)
State the problem and the solution for acid rain (also talk about which hydroxide is used in the solution)
- Acid rain can cause soil to become acidic and this can affect crop production/health of plant life
- Calcium hydroxide, Ca(OH)2 can be added to neutralise the soil
State another use for a different hydroxide
Magnesium hydroxide, Mg(OH)2 is found in indigestion tablets as an antacid.
What is the general reaction between a metal and a halogen?
Metal + Halogen → Metal Halide (salt)
e. g. Sodium + Chlorine → Sodium Chloride
e. g. Potassium + Bromine → Potassium Bromide
What a displacement reaction?
A reaction where an element in a compound is replaced by another element which is more reactive
In the reaction between Chlorine and Potassium Bromide will displacement occur?
Yes displacement will occur as chlorine is more reactive than Bromine
In the reaction between Iodine and Potassium Fluoride will displacement occur?
No because, Fluorine is more reactive than Iodine
Write the half equation for Fluorine
2F- → F2 + 2e-
Where F = Fluorine
e- = Electron
F- = Fluorine ion
Write the half equation for Chlorine
2Cl- → Cl2 + 2e-
Where Cl = Chlorine
e- = Electron
Cl- = Chlorine ion
In reactions where there is NO displacement will oxidation or reduction occur?
No!
State the reaction between Chlorine and Water and state what gets oxidised and what gets reduced
Cl2 (g) + H20 (l) ⇌ HCl (aq) + HOCl
Chlorine gets reduced from 0 to -1
Chlorine also gets oxidised from 0 to +1
What is a disproportionation reaction?
A reaction where a species (element) is both oxidisied and reduced
State a few uses of Chlorine
Chlorine - Water purification, Solvents and bleach
Evaluate the pros and cons of using chlorine
Pros : Water purification,
Cons : Chlorine can react with organic matter in water such as bits of leaves to form new chemicals. It has been suggested that these chemicals may lead to the formation of some cancers. However, there is not enough evidence to prove a strong link between the 2
What does soluble mean?
Dissolves in water e.g. NaCl
What does insoluble mean?
Does not dissolve in water e.g. Copper hydroxide
What is a cation? What is an anion?
A cation is a position and an anion is a negative ion
Show the reaction between aqueous sodium hydroxide and chlorine
Cl2 (g) + 2NaOH (aq) → NaCl + NaClO (bleach) + H20
Chlorine gets oxidised from 0 to +1
Chlorine gets reduced from 0 to -1
Describe the halide ion of Chlorine (Cl-)
What precipitate (ppt) is formed with AgNO3 ?
Does the ppt dissolve with dilute ammonia (NH3) ?
Does the ppt dissolved with concentrated ammonia?
White precipitate
Dissolves in dilute ammonia
Dissolves in concentrated ammonia
Describe the halide ion of Bromine (Br-)
What precipitate (ppt) is formed with AgNO3 ?
Does the ppt dissolve with dilute ammonia (NH3) ?
Does the ppt dissolved with concentrated ammonia?
Cream coloured precipitate
Does NOT dissolve in dilute ammonia
Does dissolve in conc. ammonia
Describe the halide ion of Iodine (I-)
What precipitate (ppt) is formed with AgNO3 ?
Does the ppt dissolve with dilute ammonia (NH3) ?
Does the ppt dissolved with concentrated ammonia?
Yellow precipitate
Does NOT dissolve in dilute ammonia
Does NOT dissolve in conc. ammonia
Write the ionic equation for the following (and state the colour change) :
1) Chlorine oxidises bromide ions to bromine
Cl2 + Br- →
2) Chlorine oxidises iodide ions to Iodine
Cl2 + I- →
3) Bromine oxidises iodide ions to iodine
Br2 + I- →
Cl2 + Br- → 2Cl- + Br2 (Green to Orange)
Cl2 + I- → 2Cl- + I2 (Green to Violet)
Br2 + I- → 2Br- + I2 (Orange to Violet)
Show the symbol equations between silver nitrate and the halogens, include state symbols
Ag+ (aq) + Cl- (aq) → AgCl (s)
Ag+ (aq) + Br- (aq) → AgBr (s)
Ag+ (aq) + I- (aq) → AgI (s)
