Topic 6- Groups In The Periodic Table Flashcards
Where are the alkali metals found on the periodic table ?
Elements found in Group 1 (found on the left-hand side of the periodic table)
How many outer shell electrons does an alkali metal have ?
Their outer shell has 1 electron in it, which is usually given away in chemical reactions
What is lithium’s electron configuration (structure) ?
Lithium has the electron structure (2,1).
What is the least reactive if the alkali metals ?
Lithium is the least reactive of the alkali metals
When lithium burns with oxygen what is the colour of the flame ?
Lithium burns with a crimson flame when it reacts with oxygen.
What will be released when lithium floats in the surface of water ?
Lithium floats on the surface of water and will release bubbles of hydrogen gas (it effervesces)
What is sodium’s electron configuration (structure) ?
Sodium has the electron structure (2,8,1).
Why is sodium more reactive than lithium?
Sodium is more reactive than lithium because its outer electron is less strongly attracted to the positively charged nucleus. This is because it is a greater distance from the positive charge of the atom’s nucleus.
What colour is the flame when sodium reacts with oxygen ?
Sodium burns with a yellow/orange flame when it reacts with oxygen.
What happens when sodium is on the surface of water ?
The metal floats on the surface of water, which releases enough heat to melt the sodium. The sodium moves quickly across the surface of the water.
What is the electron configuration (structure) of potassium ?
Potassium has the electron structure (2,8,8,1).
Why is potassium more reactive than lithium and sodium ?
Potassium is more reactive than lithium and sodium because its outer electron is least strongly attracted to the nucleus.
What is the colour of the flame when potassium reacts with oxygen?
Potassium burns with a lilac flame when it reacts with oxygen
What happens when potassium floats on the surface of water ?
The metal floats on the surface of water, and has a similar, but more vigorous, reaction compared with sodium
What do all group 1 (and 2) elements end with?
ium
Lithium
Potassium
Sodium
What are the properties of alkali metals (group 1) ?
All of the elements in Group 1 have 1 electron in their outer shell.
These metals are very reactive because they easily lose the electron in their outer shell.
All react with:
Chlorine
Water
Oxygen
What happens when a metal alkali reacts with chlorine ?
A metal chloride is formed (e.g. sodium chloride), which dissolves in water to give a colourless solution
What happens when an alkali metal reacts with water ?
The metal floats on the surface and melts to create a metal hydroxide (e.g. lithium hydroxide).
When they react with water, the energy released is enough to melt the metal.
What happens when an alkali metal reacts with oxygen ?
Rapidly turns from silvery shiny to dull as a metal oxide (e.g. potassium oxide) is produced
As you move down group 1 of the periodic table, the reactions of alkali metals become quicker and more vigorous. Why is this ?
Distance - The number of electron shells increases meaning there is a greater distance between the outer electron and the nucleus
Strength of attraction - The greater the distance between the outer electron and the nucleus, the weaker the attraction between them
Reactivity - The weaker the attraction between the outer electron and the nucleus, the easier it is for the outer electron to be lost
What do Potassium, sodium and lithium all react quickly with cold water to produce what ?
a metal hydroxide and hydrogen gas
What happens when potassium reacts with cold water ?
Potassium is the most reactive so reacts very quickly.
The hydrogen produced ignites instantly and the metal also sets alight, sparking and burning with a lilac flame
What happens when sodium reacts with cold water ?
Sodium fizzes rapidly and melts to form a ball that moves around on the water surface.
What happens when lithium reacts with cold water ?
Lithium fizzes steadily and floats, becoming smaller until it eventually disappears
As you go down the group, the reactions become quicker and more vigorous. Why is this ?
Electron shells - The atoms gain more electron shells as you go down group 1.
This means there are more electron shells in between the nucleus and outer electron, which shields the electron from the nuclear charge.
This means that the electron is more easily lost, so the atom is more reactive.
Weaker attraction - The attraction between the positive nucleus and negative outer electron becomes weaker as you go down the group because the outer electron is further from the nucleus.
Metal + water —> ? + ?
Metal + water —> metal hydroxide + hydrogen
What are Elements in group 7 of the periodic table called ?
Elements in group 7 in the periodic table are called halogens
How many outer shell electrons do group 7 elements (halogens) have ?
They have 7 electrons in their outer shell
Why are group 7 elements (halogens) very reactive ?
They are very reactive because they easily accept an electron into this outer shell.
They have similar properties and react in similar ways.
When halogens react how many electrons do they gain and why ?
They gain 1 electron to get a full outer shell
By gaining 1 electron they become a negative ion
In their elemental form, halogens share electrons to make what ?
diatomic molecules (molecules made of pairs of atoms).
When a metal transfers it’s outer electron to a non-metal atom (like a group 7 atom) what is formed ?
salts are formed
The result is a compound where all the ions have a full outer shell
As you go down the group, the halogens become less reactive. Why is this ?
The atoms gain more electron shells.
The outer electron shell is further from the nucleus.
The attraction between the nucleus and the electron (to be gained from another element) decreases.
What are three types of halogens ?
Chlorine
Iodine
Bromine
At room temperature what is the colour and state of chlorine ?
Colour: pale green
State: gas
At room temperature what is the colour and state of iodine ?
Colour: dark grey
State: solid
At room temperature what is the colour and state of bromine ?
Colour: red-brown
State: liquid
How do you test for chlorine (practical) ?
Insert damp litmus paper into a test tube containing a gas.
If the gas is chlorine, the litmus paper will bleach and change colour from red to white
What are the elements in group 0 called ?
Noble gases
Why are noble gases inert (unreactive) ?
The elements in Group 0 are unreactive because they have a full outer electron shell. They do NOT gain or lose electrons to fill up this shell as it is already full.
Why can noble gases be used in light bulbs ?
Noble gases can be used in light bulbs because they will NOT react with the hot metal filament.
Why are noble gases monatomic ?
Because noble gases are unreactive, they exist as single atoms (monatomic) instead of forming molecules.
Do noble gases have a high or low boiling point?
Low
Why do the boiling points of noble gases increases as you go down the periodic table?
This is because the relative atomic mass increases lower down the periodic table.
Do noble gases have a high or low density ?
The noble gases (in group 0) have low densities.
Why do the densities of the Nobel gases increase as you move down the periodic table ?
because of their increasing relative atomic mass.
Why are noble gases used in balloons ?
The low density makes them useful in balloons.
What do halogens reactive with metals to form ?
Halogens react with metals to form metal halides.
Metal halides are ionic compounds that are solid at room temperature.
The more reactive the halogen, the more ? the reaction ?
The more reactive the halogen, the more violent the reaction.
Sodium + chlorine → ?
Sodium + chlorine → sodium chloride
2Na(s) + Cl2(g) → 2NaCl(s)
Aluminium + bromine → ?
Aluminium + bromine → aluminium bromide
2Al(s) + 3Br2(l) → 2AlBr3(s)
What is the general formula for the reaction between a halogen and metal ?
metal + halogen → metal halide
What type of compounds are hydrogen halides ?
Covalent compounds
At room temperature what state are metal halides ?
Solid
What type of compounds are metal halides ?
Metal halides are ionic compounds
Hydrogen + chlorine —> ?
Hydrogen + chlorine → hydrogen chloride
H2(g) + Cl2(g) → 2HCl(g)
What do hydrogen halides dissolve in water to form ?
The hydrogen halides dissolve in water to form acidic solutions, such as hydrofluoric acid, hydrobromic acids and hydroiodic acid.
What does hydrogen chloride dissolve in water to form ?
Hydrogen chloride dissolves in water to form hydrochloric acid.
The solutions produce H+ ions, which make them acidic.
More reactive substances can displace (replace) less reactive substances from compounds. What is this called ?
Displacement
The displacement reaction creates what ?
Sodium bromide + chlorine → ?
sodium chloride + bromine
2NaBr + Cl2 → 2NaCl + Br2
Chlorine can displace bromine from a compound because it is more reactive.
What is oxidation ?
Electrons are lost
What’s an example of oxidation ?
Bromide ions are oxidised (electrons are lost):
2Br- → Br2 +2e-.
What is reduction ?
Electrons are gained
What’s an example of reduction ?
Chlorine is reduced (electrons are gained):
Cl2 + 2e- → 2Cl-.
What are spectator ions ?
ions that do not change in the reaction, so we call them spectator ions
What’s an example of a displacement reaction ?
Use the example when chlorine reacts with sodium bromide
More reactive substances can remove less reactive substances from compounds. In this example, when chlorine reacts with sodium bromide, the products are sodium chloride and bromine. We say that chlorine has displaced bromine.
2NaBr(aq) + Cl2(g) → 2NaCl(aq) + Br2(l)
What are the spectator ions in this reaction ?
Na+
What type of reaction is a displacement reaction ?
Redox reaction
Which group of elements form DIATOMIC MOLECULES and become LESS REACTIVE as you move down the group?
Group 7
Experiment A
Cl2(g) is bubbled through a solution of NaBr. An orange colour develops as bromine is produced.
Explain the observations or lack of observations. Write equations for any reactions that occur.
Chlorine displaces the bromide ions in NaBr. This leads to the formation of bromine which is orange.
Cl2 + 2NaBr → Br2 + 2NaCl
Experiment B
Br2(g) is bubbled through a solution of NaCl. No observations are made.
Explain the observations or lack of observations. Write equations for any reactions that occur.
There are no observations is experiment B because bromine cannot displace the chloride ions in NaCl.
A scientist conducts 2 experiments.
Experiment A
Cl2(g) is bubbled through a solution of NaBr. An orange colour develops as bromine is produced.
Experiment B
Br2(g) is bubbled through a solution of NaCl. No observations are made.
Explain the observations or lack of observations. Write equations for any reactions that occur.
Explain the results
This is because reactivity decreases down group 7. Bromine is lower down than chlorine and is, therefore, less reactive and cannot displace.
Explain why reactivity decreases down group 7
The difference in the atoms
- Going down the group, atoms get bigger.
- The outer electrons are, therefore, further from the nucleus.
- This means the attraction between the negatively charged electrons and the positively charged nucleus are less strong.
The difference in reactivity
- Group 7 elements react to become ions with a 1- charge. This means they gain 1 electron.
- Down the group, there is less attraction for the outer electrons. This means that the elements gain electrons less easily.
