GCSE Topic 6 - Periodic table Flashcards
Cation
Positively charge ion, such as Na+
Anion
Negatively charge ion, such as Cl-
What happens to group 1 metals in a reaction, in terms of electrons?
Group 1 metal atoms lose 1 electron to become a cation with a charge of 1+
What happens to group 2 metals in a reaction, in terms of electrons?
Group 2 metal atoms lose 2 electrons to become a cation with a charge of 2+
What happens to group 3 metals in a reaction, in terms of electrons?
Group 3 metal atoms lose 3 electron to become a cation with a charge of 3+
What happens to group 5 non-metals in a reaction, in terms of electrons?
Group 5 non-metal atoms in a molecule each gain 3 electrons to become a cation with a charge of 3-
What happens to group 6 non-metals in a reaction, in terms of electrons?
Group 6 non-metal atoms in a molecule each gain 2 electrons to become a cation with a charge of 2-
What happens to group 7 non-metals in a reaction, in terms of electrons?
Group 7 non-metal atoms in a molecule each gain 1 electron to become a cation with a charge of 1-
Oxidation, in terms of electrons
Loss of electrons
Reduction, in terms of electrons
Gain of electrons
Redox reaction
A reaction where one substance is oxidised and another substance is reduced.
Trend in reactivity of group 1 metals
Reactivity increases down the group
Explanation for the trend in reactivity of group 1 metals
This would be a grade 9 answer
- Reactivity increases down the group
- This is because atomic radius increases
- So the distance between the positive nucleus and negative outer electron increases
- Number of shells increases
- So electron shielding increases
- Both of these factors cause the electrostatic attraction between the nucleus and outer electron to decrease
- So the metal atom more easily loses its outer electron
- And is more easily oxidized
Symbol equation for the reaction of lithium with water
2 Li (s) + 2 H2O (l) → 2 LiOH (aq) + H2 (g)
Symbol equation for the reaction of sodium with water
2 Na (s) + 2 H2O (l) → 2 NaOH (aq) + H2 (g)
Symbol equation for the reaction of potassium with water
2 K (s) + 2 H2O (l) → 2KOH (aq) + H2 (g)
Symbol equation for the reaction of sodium with oxygen
2 Na (s) + O2 (g) → Na2O (s)
Symbol equation for the reaction of potassium with oxygen
2 K (s) + O2 (g) → K2O (s)
Symbol equation for the reaction of magnesium with oxygen
2 Mg (s) + O2 (g) → 2 MgO (s)
Symbol equation for the reaction of sodium with chlorine
2 Na (s) + Cl2 (g) → 2 NaCl (s)
Symbol equation for the reaction of potassium with chlorine
2 K (s) + Cl2 (g) → 2 KCl (s)
Type of reaction between a metal and a non-metal
Redox reaction
pH of a potassium hydroxide solution
pH 12 to 14
Strongly alkaline
Ion that makes solutions alkaline
Hydroxide ion
OH- (aq)
Half equation for the reactions of sodium
Na → Na+ + e-
Half equation for the reactions of chlorine
Cl2 + 2 e- → 2 Cl-
Observations for the reaction of lithium with water
- Effervescence
- Lithium floats on the surface (it has half the density of water)
Observations for the reaction of sodium with water
- Effervescence
- Sodium melts into a ball
Observations for the reaction of potassium with water
- Effervescence
- Potassium melts into a ball
- Lilac flame (the reaction is highly exothermic, causing the hydrogen gas to ignite)
Trend in melting points of group 1 metals
Decreases down the group
The metals can be cut with a knfe
Explanation for the trend in melting points of alkali metals
- Melting points decrease down the group
- This is because metallic bond strength decreases
- Metallic bonding is the electrostatic attraction between the cations and sea of delocalised electrons
- This electrostatic attraction gets weaker from Li to Na to K
- Because the charge density decreases
- As the charge stays the same but the atomic radius increases
Colour of potassium hydroxide solution with universal indicator
Blue
Compare the reactivity of the alkali metals with water
- General equation is 2 M (s) + 2 H2O (l) à 2 MOH (aq) + H2 (g) , where M is a group 1 metal
- Lithium, sodium and potassium all effervesce as hydrogen gas is produced
- They all react with water to produce a soluble hydroxide
- And strongly alkaline solution of pH 12 to pH14 owing to production of the hydroxide, OH- ion
- Sodium and potassium melt into a ball
- Potassium reacts with water to produce a lilac flame
- Reactivity increases from Li to Na to K
- The reactions get progressively more exothermic
- The reaction between potassium and water is sufficiently exothermic to ignite the hydrogen gas produced
Number of available electron shells for a sodium ion
Seven
Number of occupied electron shells for a sodium ion
Two
Number of occupied electron shells for a sodium atom
Three
Colour of fluorine
Yellow
Colour of chlorine
yellow-green
Colour of bromine
orange-red
Colour of solid iodine
shiny black solid
Colour of aqueous iodine
brown
Colour of iodine vapour
purple
Colour of iodine in hexane
purple
Trend in melting point for the halogens
- Increases down the group
- Fluorine is a gas
- Chlorine is a gas
- Bromine is a liquid
- Iodine is a solid
Explanation for the trend in melting point for the halogens
- Intermolecular forces become greaterr from F2 to I2
- More thermal energy is required to overcome these forces
Trend in reactivity for the halogens
Decreases down the group
Explanation for the trend in reactivity of the halogens
This would be a grade 9 answer
- Reactivity DECREASES down the group
- This is because atomic radius increases
- So the distance between the positive halogen nucleus and the negative outer electron of a NEIGHBOURING atom increases
- Number of shells increases
- So electron shielding increases
- Both of these factors cause the electrostatic attraction between the halogen nucleus and the negative outer electron of a NEIGHBOURING atom increases
- So the non-metal atom LESS easily gains an electron
- And is LESS easily reduced
Symbol equation for the reaction of fluorine with potassium chloride
F2 (g) + 2 KCl (aq) → Cl2 (g) + 2 KF (aq)
There will be NO colour change. Potassium iodide is colourless and chlorine gas dissolves in water to make a colourless solutuion, unlike bromine and iodine.
Symbol equation for the reaction of chlorine with potassium bromide
Cl2 (g) + 2 KBr (aq) → Br2 (l) + 2 KCl (aq)
There will be a colour change from colourless to orange. Note that the bromine that is produced will be dissolve in water to produce an orange solution.
Symbol equation for the reaction of chlorine with potassium iodide
Cl2 (g) + 2 KI (aq) → I2 (s) + 2 KCl (aq)
There will be a colour change from colourless to brown. Note that the iodine that is produced will be dissolve in water to produce a brown solution.
Symbol equation for the reaction of bromine with potassium iodide
Br2 (l) + 2 KI (aq) → I2 (s) + 2KBr (aq)
There will be a colour change from colourless to brown. Note that the iodine that is produced will be dissolve in water to produce a brown solution.
Ionic equation for the reaction of fluorine and potassium chloride
F2 (g) + 2 Cl- (aq) → Cl2 (g) + 2 F- (aq)
Only the molecules and ions involved in the reaction appear in the ionic equation. The other ions are spectator ions and do not take place in the reaction.
These reactions are redox reactions. The more reactive halogen is reduced, the less reactive halogen is oxidized.
Ionic equation for the reaction of chlorine and potassium bromide
Cl2 (g) + 2 Br- (aq) → Br2 (l) + 2 Cl- (aq)
Only the molecules and ions involved in the reaction appear in the ionic equation. The other ions are spectator ions and do not take place in the reaction.
These reactions are redox reactions. The more reactive halogen is reduced, the less reactive halogen is oxidized.
Ionic equation for the reaction of chlorine and potassium iodide
Cl2 (g) + 2 I- (aq) → I2 (s) + 2Cl- (aq)
Only the molecules and ions involved in the reaction appear in the ionic equation. The other ions are spectator ions and do not take place in the reaction.
These reactions are redox reactions. The more reactive halogen is reduced, the less reactive halogen is oxidized.
Ionic equation for the reaction of bromine and potassium iodide
Br2 (l) + 2 I- (aq) → I2 (s) + 2Br - (aq)
Only the molecules and ions involved in the reaction appear in the ionic equation. The other ions are spectator ions and do not take place in the reaction.
These reactions are redox reactions. The more reactive halogen is reduced, the less reactive halogen is oxidized.
Half equation for fluorine
F2 (g) + 2 e- → 2 F- (aq)
These reactions show what is happening in terms of electrons. Only ONE halogen appears in this equation.
Each halogen atom in a halogen molecule gains one electron to become a halide 1- ion.
Half equation for chlorine
Cl2 (g) + 2 e- → 2 Cl- (aq)
These reactions show what is happening in terms of electrons. Only ONE halogen appears in this equation.
Each halogen atom in a halogen molecule gains one electron to become a halide 1- ion.
Half equation for bromine
Br2 (l) + 2 e- → 2 Br- (aq)
These reactions show what is happening in terms of electrons. Only ONE halogen appears in this equation.
Each halogen atom in a halogen molecule gains one electron to become a halide 1- ion.
The least reactive group of elements
Noble gases
NOT Nobel gases
This noble gas reacts with fluorine
Xenon
Xenon tetrafluoride is formed, XeF4
This noble gas is the least reactive element
Helium
Explanation for the low reactivity of the noble gases
The atoms have a full outer shell of electrons
Uses of noble gases
- Flammable or highly reactive liquids are placed in a container with an atmosphere of a noble gas
- Fill balloons with helium as its density is a lot less than the density of air
Trend in boiling point for the noble gases
Increases down the group