C4.1 - Predicting Chemical Reactions Flashcards
(36 cards)
Why are group 1 metals called the alkali metals?
Group 1 metals are called the alkali metals because they react with water to form alkaline solutions.
What are some properties of the alkali metals?
- Have some typical properties of metals.
- Shiny when freshly cut.
- Good conductors of electricity.
- Solid state at room temperature.
- Group 1 elements are soft enough to cut
with a knife. - Each alkali metal is softer as you go down
the group.
What are the trends of group 1 metals?
- Going down the group - Their density increases,
although sodium is denser than expected. - Going down the group - Their melting point
decreases. - Going down the group - Their reactivity increases.
Why are the alkali metals stored in oil?
The alkali metals are stored in oil because they react rapidly with the 1oxygen in the air and with water.
What happens when an alkali metal reacts with water?
Alkali metal + Water -> Metal hydroxide + Hydrogen
Describe the reaction of the alkali metals and water.
- Lithium fizzes steadily and slowly disappears.
- Sodium melts to form a silvery ball, fizzes
vigorously, and quickly disappears. - Potassium immediately ignites, burns with a lilac
flame, and very quickly disappears.
Why do group 1 elements have similar chemical properties?
All group 1 elements atoms have 1 electron in their outer shell which they lose in a reaction to leave a complete outer shell forming ions with a single positive charge.
Why does the reactivity of alkali metals increase as you go down the group?
- There is an increased distance between the electron and nucleus. - More shielding. - It is easier to lose an electron. - Therefore it is more reactive.
Why does density increase as you go down an elements group?
- There are more protons and neutrons as you go
down the group. - Even though the atoms are bigger, the mass
increases even more. - Therefore, there is a greater mass per unit volume
which means a higher density.
Why does melting point decrease as you go down the group 1?
- Metallic bonds are weaker.
- Because there is a greater distance between
the nucleus and the electrons. - Therefore, less energy is needed to break the
bonds between the atoms.
Give the three symbol equations with reactions relating to alkali metals.
- 2M + 2H2O -> 2MOH + H2
- 4M + O2 -> 2M2O
- M -> M+ + e-
What are group 7 elements known as are what are their properties?
- Group 7 elements are known as the halogens.
- They have typical properties of non -
metals. - Brittle in solid state.
- Poor conductors of electricity.
How do group 7 elements exist?
- Diatomic molecules.
- Weak intermolecular forces.
- Coloured or form coloured vapours.
- Occur in different states at room temperature.
What are the colours and states (at room temperature) for the group 7 elements?
- Fluorine is a pale yellow gas.
- Chlorine is a green gas.
- Bromine is an orange-brown liquid that
vaporises easily. - Iodine is a shine grey-black crystalline solid that
sublimes to form a purple vapour.
What are the trends going down group 7?
- Density increases.
- Melting and boiling points increase.
- Reactivity decreases.
Why does the melting and boiling points of the halogens increase as you go down the group?
- The molecules are bigger.
- Therefore the intermolecular forces are stronger
and more energy is required to break them.
Why do the halogens all have similar chemical properties?
- All halogens have 7 electrons in their outer
shell. - They all gain an electron in their outer shell
forming ions with a single negative charge.
Why does reactivity decrease as you go down group 7?
- Halogens are trying to gain an electron to
complete its outer shell. - As you go down the group, it is harder to gain
an electron because the nuclear attraction is
weaker as there is more shielding.
Why are group 7 elements called the halogens?
- They react with metals to produce salts.
- They also react vigorously with group 1 metals,
particularly if the metal is heated first.
Give the two symbol equations relating to the halogens.
- 2M + X2 -> 2MX
- X2 + 2e- -> 2X-
What is a halide and halide ions?
- A halide is a compound of a group 7 element and
one other element (usually a hydrogen or metal). - A halide ion is a negative ion formed by a group 7
element.
Describe what is a halogen displacement reaction and which halogens displace which.
- A halogen will displace a less reactive halogen
from its halide ions in solution. - Chlorine displaces bromine from bromides, and
iodine from iodides. - Bromine displaces iodine from iodides but not
chlorine from chlorides. - Iodine cannot displace chlorine from chlorides or
bromine from bromides.
Describe the steps to carry out a halogen displacement reaction.
- Wearing eye protection place a small volume of
potassium chloride, potassium bromide, and
potassium iodide in each all 9 spaces of a three
by three spotting tile. - Add a few drops of chlorine solution across the
first row, a few drops of bromine across the
second row and a few drops of iodine across
the third row. - Note your observations in a table.
- Asthmatics should take particular care not to
breathe in any chemical fumes.
What are group 0 elements called and why?
The elements in group 0 are called the noble gases because they are so unreactive.
