C4 Flashcards
What are group 1 elements like?
Group 1 elements are placed in the vertical column on the far left of the periodic table.
-they are called alkali metals because they react with water to form alkaline solutions.
-group 1 elements have some typical properties of metals.
-They are shiny when freshly cut
-They are good conductors of electricity
-but they also have some unusual properties
-The alkali metals are in the solid state at room temperature, but they are all soft enough to cut with a knife. Lithium is the hardest and each alkali metal is softer as you go down the group
-A general pattern of direction of change is a trend.
-The alkali metals show other trends in their physical properties.
Going down the group:
-Their density increases, although sodium is denser than expected
-Their melting point decreases
What elements are in group 1 ( ascending order) :
Li -Lithium
Na -Sodium
K -Potassium
Rb -Rubidium
Cs -Caesium
Fr -Francium
Why are lithium, sodium and potassium stored in oil?
They react very quickly with oxygen
How do alkali metals react with water?
The alkali metals react with water to produce the metal hydroxide and hydrogen. For example, sodium reacts with water to produce sodium hydroxide and hydrogen:
2Na(s) + 2H2O(l) —> 2NaOH(aq) +H2(g)
The reactivity of alkali metals with water increases down the group:
-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.
How do you explain the trend in reactivity
The group 1 elements have similar chemical proper because all of their atoms have one electron in their outer shell. They lose these outer electrons in reactions, leaving a complete outer shell and forming ions with a single positive charge.
This general ionic equation models the change (M stands for the symbol of the metal):
M—> M^+ + e^-
The easier it is for an atom of a group 1 element to lose its outer electron, the more reactive the element is.
For example potassium is more reactive than lithium because it’s atoms lose their outer electron more easily than lithium atoms do.
What are the group 7 elements like?
The elements in group 7 are placed in a vertical column on the right of the periodic table. They have typical properties of non-metals, including being brittle in the solid state and poor conductors of electricity.
Group 7 elements exist as diatomic molecules with weak intermolecular forces. They are coloured or form coloured vapours and they occur in different states at room temperature:
Fluorine, F2, is a pale yellow gas
Chlorine, Cl2, is a green gas
Bromine, Br2, is an orange-brown liquid that vaporises easily
Iodine, I2, is a shiny grey-black crystalline solid that sublimes to form a purple vapour
Going down group 7:
-Density increases
-Melting points and boiling points increase
What is fluorine like at room temperature?
Fluorine,F2, is a pale yellow gas
What is chlorine like at room temperature?
Chlorine,Cl2, is a green gas
What is bromine like at room temperature?
Bromine,Br2, is an orange-brown liquid that vaporises easily
What is iodine like at room temperature?
Iodine,I2, is a shiny grey-black crystalline solid that sublimes to form a purple vapour.
What are the reactions of group 7 elements?
Group 7 elements are also called the halogens because they react with metals to produce salts. They react vigorously with group 1 metals, particularly if the metal is heated first. For example sodium reacts with chlorine to produce sodium chloride:
2Na(l) + Cl2(g) —> NaCl(s)
The reactivity of the halogens decreases down the group.
This is the opposite trend in reactivity to the alkali metals.
How do you explain the trend in reactivity of group 7 elements?
The halogens have similar chemical properties because all of their elements have seven electrons in their outer shell. They gain an electron in reactions, completing their outer shell and forming ions with a single negative charge.
This general ionic equation models the change(X stands for the symbol of the halogen):
X2 + 2e^- —> 2X^-
The easier it is for a halogen atom to gain an outer electron, the more reactive the element is. For example, chlorine is more reactive than iodine because its atoms gain an outer electron more easily than iodine atoms do
What does halogen mean?
The word halogen comes from the Greek word halos, meaning salt. The gen part means maker. (salt maker)
What is a halogen displacement reaction?
Halogens can react with halides in solution. A halide is a compound containing a group 7 element and one other element, usually hydrogen or metal.
For example, chlorine reacts with sodium bromide solution to form sodium chloride and bromine
Cl(g) + 2NaBr(aq) —> 2NaCl(aq) + Br2 (aq)
The reaction mixture turns orange-brown as bromine is produced. Chlorine can displace or push out bromine from sodium bromide in a displacement reaction.
A halogen will displace a less reactive halogen from its halide ions in solution.
That means that:
-Chlorine displaces bromine from bromides, and iodine from iodides
-Bromine displaces iodine from iodides, but it cannot displace chlorine from chlorides
-Iodine cannot displace chlorine from chlorides, or bromine from bromides.
It is safer in school to use aqueous solutions of chlorine, bromine and iodine rather than pure elements.
Halogen displacement reactions:
You can use halogen displacement reactions to confirm the order of reactivity for chlorine, bromine and iodine.
1- wearing eye protection l, place a small volume of potassium chloride solution in a spotting tile well.
2-Add a few drops of bromine water.
3-Note your observations in a table.
4-You will then need to repeat this for other pairs of solutions.
How can ionic equations model displacement reactions?
You can write a half equation to model what happens to each reactant.
For example, chlorine displaces bromine from bromide ions:
Cl2 + 2e^- —> 2Cl^- : reduction
2Br^- —> Br2 + 2e^- : oxidation
You can combine half equations to make the ionic equation:
Cl2 + 2Br^- —> 2Cl^- + Br2
What are the group 0 elements like?
The laments in group 0 are placed in a vertical column on the far right of the periodic table. They are called the noble gases because they are so unreactive. Rather like the “noble” men and women of the past who did not take part in ordinary everyday activities, the noble gases take part in very few chemical reactions. The group 0 elements are non-metals, and all re in the gas state at room temperature.
Why are the noble gases so unreactive?
The atoms of group 0 elements have complete outer electron shells. This means that they have no tendency to lose or gain electrons to form ions in reactions, or to share electrons to form molecules in reactions. As a result, the noble gases are very unreactive.
What trends in properties do the noble gases show?
The noble gases are monatomic. They exist as single atoms with very weak forces of attraction between them. These forces are easily overcome by heating.
This gives the noble gases very low boiling point.
Going down group 0:
-The attractive forces between atoms get stronger
-The boiling point increases
The noble gases have very low densities. This is because their atoms are far apart in the gas state, so there is very little mass in a given volume. As you go down group 0, the density increases.
What are the transition metals like?
The transition metals are placed between groups 2 and 3 (groups 2 and 13) in the periodic table, occupying groups 3 to 12. They are all metals and their properties are typical of metals. In general,they are:
-Shiny when freshly cut
-good conductors of electricity
-strong
-malleable (they can be bent or hammered into shape)
