SC17 - Groups in the Periodic Table ✓
No description yet. This curated deck is ready for daily study.
Card preview (24)
SC17a - What are the physical properties of the alkali metals (group 1)
• Malleable • Good conductors of electricity • Relatively low melting points • Soft/easily cut
SC17a - Why are alkali metals stored in oil?
They are incredibly reactive and would react with the oxygen and moisture in air otherwise.
SC17a - When you cut an alkali metal, a layer of tarnish forms. What is this called and what is the equation for this?
This is oxidation. 4x(s) + O2(g) -> 2x2O(s) Metal + Oxygen → Metal Oxide [Where x is any alkali metal]
SC17a - How does the melting point of the alkali metals change as you go down?
It decreases
SC17a - What is the equation for the reaction that takes place when an alkai metal reacts with water?
2x(s) + 2H2O(l) → 2xOH(aq) + H2(g)
SC17a - What would you observe when you put lithium, sodium and potassium in water that contains universal indicator?
• Li: Bubbling fiercely on the surface and moves around a bit. Water turns purple • Na: Melts into a ball and fizzes about the surface Water turns purple • K: Bursts into flames and flies about the surface. Water turns purple. • Effervesance/bubbling indicates the presence of a gas (hydrogen) • Water turns purple becuase it is alkali. • Increased speed indicates a higher rate of reaction
SC17a - What happens to the reactivity of alkali metals as you go down?
It increases.
SC17a - The reactivity of alkali metals increases as you go down the table. Explain why this is using Lithium and Potassium as examples.
• Both Lithium and Potassium want to loose their only outer shell electron to gain a full outer shell and become stable • Potassium has more shells of electrons and so there are more shells between its positive nucleus and its outer most electron • The shells in between shield the positive charge • Additionally it is urther away from the nucleus • The positive charge from Lithium’s outermost electron is shielded by less shells and so the electrostatic forces of attraction to its outer shell electron are stronger • As Potassium has weaker electrostatic forces of attraction to its outer shell electron, this electron can be los tmore easily • This means Potassium will be more willing to loose its electron to form an ion making it more reactive. • Thus as you go down the group, every extra layer of electron shells makes the element more reactive
SC17b - What is the name for group 7 elements and what is key about their natural state?
• The halogens. • They exist covalently bonded as diatomic atoms.
SC17b - What is fromed when a halogen reacts with a metal (e.g. Chlorine and Magnesium)?
• It forms a halide salt. • Cl2(g) + Mg(s) → MgCl2(s)
SC17b - What happens to the name of a halogen once it it becomes an ion?
• It changes from -ine to -ide • e.g. BromiNe atom to BromiDe ion
SC17b - What is the trend in mp/bp and density of halogens as you go down the group?
It increases.
SC17b - What are the appearances of Chlorine, Bromine and Iodine at room temperature?
• Cl: Green gas • Br: Brown liquid • I:Purple/grey solid
SC17b - What are the properties of Halogen gases?
• Non-metals • Diatomic • Toxic • Corrosive • Brittle when solid • Low mp/bp • Poor conductors of electricity and heat • Coloured vapours
SC17b - What is the common use for all the halogens?
As disinfectancs/bleaches as they can kill microorganisms and remove stains.
SC17b - Using Hydrogen and Chlorine as examples explain how halogen gases cna be used to from acidic solutions.
• Hydrogen and chlorine molecules collide and the covalent bonds holding the atoms together break • Covalent bonds form between hydrogen and chlorine atoms, making a new compound of hydrogen chloride • When hydrogen chloride dissolves in water, the molecules break up into two ions, H+ and Cl-. The formation of H+ ions makes solution acidic
SC17b - What is the test for chlorine?
Damp blue litmus paper will turn red and bleach white in the presence of chlorine gas.
SC17c - What observations will you make when you heat halogens with iron wool and what does this tell you about the reactivity trend?
• Fluorine: Bursts into flames • Chlorine: Glows brightly • Bromine: Glows dull red • Iodine: Changes colour • As the reaction gets less violent as you go down the group you can tell that they get less reactive.
SC17c - What is a displacement reaction?
A reaction in which a more reactive element displaces a less reactive metal from a compound producing the less reactive metal
SC17c - State what observation you would make in each of these reactions signifying that displacement has taken place: • Fluorine + Potassium chloride • Chlorine + Potassium bromide • Potassium bromide+ iodide
• Solution turns yellow showing that chlorine has been produced • Solution turns orangey-brown showing that bromine has been produced • Solution turns dark brown showing that iodine has been produced
SC17c - Why is displacement a redox reaction?
• Because both oxidation and reduction occur at the same time. • e.g 2Cl- + F2 → Cl2 + F- • The chlorine looses electrons at the same time that the fluorine gains electrons and so it is a redox reaction
SC17c - Using Fluorine and Iodine as examples explain why the reactivity of halogens decreases as you go down the group?
• Both Fluorine and Iodine want to gain one outer shell electron to have a full outer shell and become stable • Iodine has more shells of electrons and so there are more shells between its positive nucleus and its outer most electron • The shells in between shield the positive charge • Additionally it is further away from the nucleus • The positive charge from Fluorine’s outermost electron is shielded by less shells and so the electrostatic forces of attraction to its outer shell electron are stronger • As Fluorine has stronger electrostatic forces of attraction to its outer shell electron, the last needed electron is attracted more easily • This means Fluorine will be more willing to gain an electron to form an ion making it more reactive. • Thus as you go down the group, every extra layer of electron shells makes the element less reactive as there is more shielding and it’s harder to gain an electron
SC17d - What is another name for the group 0 elements?
Group 8 / Noble gases
SC17d - What are the properties of the noble gases?
• Colourless • Have very low m.p/b.p • Poor conductros of heat and electricity • Inert/unreactive