Recall the physical and chemical properties of groups 1, 7 & 0 Flashcards
What are group 1 metals known as
The alkali metals
Why do alkali metals all have similar chemical properties
- They all have one electron in the outer shell
What are the physical properties of alkali metals
- Low melting and boiling points compared to other metals
- low density - Li, Na, K float on water
- Very soft - they can be cut with a knife
Why are group 1 metals reactive?
- They readily lose their one outer electron to form a +1 ion to get a stable electronic structure
- as you go down group 1 the alkali metals get more reactive
- because outer electron is easily lost because the atomic radius is larger
- therefore it’s less strongly attracted to nucleus and less energy needed to remove it
Describe the reaction between a alkali metal and cold water
- Reacts vigorously
- produces metal hydroxide + hydrogen
describe the reaction between rubidium and cesium with water
- react violently with watee and explode
what is the balanced equation of sodium + water
2Na+2H2O→2NaOH+H2
What are the group trends for group 1
Down the group:
- increasing atomic radius
- decreasing electronegativity
- increasing reactivity
- decreasing melting and boiling pointsincreasing atomic radius
What would you see when lithium reacts with water
- When lithium is added to wafter it floats.
- It fizzes steadily and becomes smaller, until it eventually disappears.
What is the word and symbol equation for lithium reacting with water
- lithium + water → lithium hydroxide + hydrogen
- 2Li(s) + 2H2O(l) → 2LiOH(aq) + H2(g)
What would you see if sodium reacted with water
- the sodium melts to form a ball that moves around on the surface
- It fizzes rapidly
- produces hydrogen that may burn with an orange flame before the sodium disappears.
What is the word and symbol equation of sodium reacting with water
- sodium + water → sodium hydroxide + hydrogen
- 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
What would you see if potassium reacted with water
When potassium is added to water
- It melts and floats around very quickly on the surface of the water.
- The hydrogen ignites instantly.
- The metal is also set on fire, with sparks and a lilac flame.
- There is sometimes a small explosion at the end of the reaction.
What is the word and symbol equation for potassium reacting with water
- potassium + water → potassium hydroxide + hydrogen
- 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
what are group 7 elements known as?
the halogens
what are the elements on group 7
- fluorine
- chlorine
- bromine
- iodine
- astatine
why do group 7 elements exist as diatomic molecules?
because they share a pair of electrons in a covalent bond giving both toms a full outer shell
what happens as you go down group seven ?
- melting and boiling points increase
- reactivity decreases
- Color becomes darker
- State of change gas to liquid to solid
at room temperature what color is
- chlorine
- bromine
- iodine
- chlorine: fairly reactive, poisonous green gas
- bromine: poisonous brown orange liquids gives off an orange vapor at room temp
- iodine: dark grey solid purple vapor when heated
why does reactivity decrease going down group 7
- gain one electron to 1- ion
- as you go down the group, less reactive as it gets harder to gain extra electron to make full outer shell when its further away form the nucleuas
what happens when halogens react with alkali metals
- form salts called metal halides
- eg : sodium+ chlorine → sodium chloride | 2Na+Cl2 → 2NaCl
- eg: potassium + bromine → potassium bromide | 2K+Br2→ 2KBr
what is a displacement reaction?
- a displacement reaction is where a more reactive element displaces a less reactive element from a compound
describe what happens in the chlorine water and potassium bromide practical
- chlorine is more reactive than bromine
- if you add chlorine water to potassium bromide
- chlorine will displace the bromine and becomes potassium chloride
- the bromide ions are oxidized to bromine turning orange
write a balanced equation for chlorine and potassium bromide displacement reaction
chlorine + sodium bromide → sodium chloride + bromine
Cl2(aq) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq)
how can displacement reactions show reactivity trends
- start by adding small amount of halide solution in test tube
- add a few drops of a halogen solution to it and shake tube gently
- color change=reaction
- the halogen replaced the halide ions from salt
- no color change no reaction
explain what is happening and what is made
when chlorine water is added to:
- potassium bromide solution-an orange solution is formed
- potassium iodide solution - a brown solution is formed
when bromine water is added to:
- potassium iodide solution- a brown solution is formed
- chlorine displaces both bromine and iodine . bromine only displaces iodine . Iodine doesn’t displace either
Florine reaction with iron wool
- Reacts with almost anything instantly.
- dangerous
Chlorine reaction with iron wool
Reacts with heated iron wool very quickly.
Bromine reaction with iron wool
Has to be warmed and the iron wool heated. The reaction is faster.
Iodine reaction with iron wool
Has to be heated strongly and so does the iron wool. The reaction is slow
Why do boiling and melting points increase as you go doen group 7
- the molecules become larger
- the intermolecular forces become stronger
- more energy is needed to overcome these forces
What is made when a halogen reacts with a non metal
use chlorine and hydrogen
- A compound is formed
- hydrogen + chlorine → hydrogen chloride
- H2(g) + Cl2(g) → 2HCl(g)
Describe the reaction between hydrogen and Florine
- Explodes at room temperature and in the dark, forming hydrogen fluoride
Describe the reaction between hydrogen and chlorine
Explodes with a flame or in sunlight, forming hydrogen chloride
Describe the reaction between hydrogen and bromine
- Vigorous reaction when warmed with hydrogen, forming hydrogen bromide
Describe the reaction between hydrogen and iodine
- Very slow reaction when heated strongly, forming some hydrogen iodide
What happens when the hydrogen halides are put into water
The hydrogen halides are gases at room temperature. They dissolve** in water to produce **acidic** **solutions.
what is group zero known as
- the noble gasses
at room temperature what color are all of the gasses ?
colorless
why are the noble gasses all monotonic
- because they’re all made up of single atoms
why are the noble gasses inert (unreactive)
- because they all have full outer shells
- meaning they dont give or gain electrons easily
why are the noble gasses non flammable
because they are inert
name the group zero elements
- helium
- neon
- argon
- krypton
- xenon
- radon
as you go down the group what happens to the
- boiling point
- melting point
- density
increase
how to estimate the densities of group 0 elements
eg use the densities of helium (0.2kg/m3) and argon (1.8kg/m2) to estimate the density of neon
- (0.2 + 1.8)/2=1
- neon should have a density around 1kg/m3
why do group 0 elements react in similar ways
- they all have full outer electron shells
