Every group in the periodic table has distinct properties and trends. In this article, we will look at group 1, found on the very left-hand side of the periodic table, and known as the alkali metals. We will cover their various properties, such as their melting and boiling points, and reactions with water and other substances.
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Jetzt kostenlos anmeldenEvery group in the periodic table has distinct properties and trends. In this article, we will look at group 1, found on the very left-hand side of the periodic table, and known as the alkali metals. We will cover their various properties, such as their melting and boiling points, and reactions with water and other substances.
The alkali metals are all of the elements in group 1 of the periodic table.
Alkali metals are lithium, sodium, potassium, rubidium, caesium, and francium. However, you will most likely only encounter the first three in school as the others are far too reactive and therefore dangerous. They are called alkali metals as when they react with water, they form an alkaline solution.
Let's see some properties of the alkali metals:
Elements in the same group have similar properties due to their electron configuration; electrons are responsible for how an element reacts and what properties they have.
All elements in group 1 have 1 electron in their outermost shell and as a result, they have similar properties.
The alkali metals are very reactive. The way an atom of any element reacts depends on its electron configuration. In all reactions, all elements want to become stable. That is their life goal! The way that atoms achieve this is by getting a full outer shell. For alkali metals which all have only 1 electron in their outer shell, the quickest way for them to obtain a full outer shell is by losing this 1 electron. This way, they are left only with the next outermost shell which is already full (remember electrons can only fill up the next shell if the previous one is completely full). Because they only need to lose 1 electron, it is very easy for an alkali metal to lose it to end up with a full outer shell, then becoming stable.
The eactivity of an element is how easily an element gets a full outer shell. The more easily an element gets a full outer shell/becomes stable, the more reactive the element is!
The alkali metals are all very reactive. Take a look at what happens when an alkali metal reacts with various substances:
In reactions, the alkali metals lose the 1 electron in their outermost shell, forming ions with a 1+ charge.
$$ Li \rightarrow Li^{+}$$
$$Na \rightarrow Na^{+}$$
$$K \rightarrow K^{+}$$
They form ionic compounds.Because the first three alkali metals have a lower density than water, they will all float. However, the reactions with water become more vigorous as you go down group 1.
Here is a table showing what happens when lithium, sodium, and potassium react individually with water.
Element | Observations | Explanations | Reaction |
Lithium |
|
| \[2Li(s) + 2H_2O(l) \rightarrow 2LiOH(aq) + H_2(g)\] |
Sodium |
|
| \[2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)\] |
Potassium |
|
| \[2K(s) + 2H_2O(l) \rightarrow 2KOH(aq) + H_2g\] |
As you can see from the reactions getting more vigorous, the reactivity increases as you go down group 1.
By the end of the reactions, all of the alkali metals dissolve in the water, producing metal hydroxides. This final solution is alkaline, which is why they are called ‘alkali metals’!
When the alkali metals react with chlorine, they react vigorously to form white metal chloride salts.
Let's see an example:
\[2Li(s) + Cl_2(g) \rightarrow 2LiCl(s)\]
\[ 2Na(s) + Cl_2(g) \rightarrow 2NaCl(s)\]
These metal chlorides dissolve easily in water to form colourless solutions.
The reactions become more vigorous as you go down the group. They react similarly with other group-7 elements (halogens) - fluorine, bromine, and iodine - to form metal halides.
The alkali metals burn vigorously with oxygen to form their metal oxides. These metal oxides are white.
\[4Na(s) + O_2(g) \rightarrow 2Na_2O(s)\]
In reactions, elements want to become stable by obtaining a full outer shell. Alkali metals do this by losing the 1 electron in their outermost shell.
Therefore, the more easily they can lose the electron in their outermost shell, the more reactive they are.
The nucleus is positively charged and the electrons are negatively charged. This electrostatic attraction keeps the electron in its shell.
Melting points and boiling points ↓
The melting points and boiling points decrease as you go down the group. Lithium has a melting point of 180.5oC compared to francium which has a melting point of only 27oC.
Densities ↑
The alkali metals become more dense as you go down the group.
Reactivity ↑
Alkali metals get more reactive as you go down the group. From the reactions with water, you can see that lithium only fizzed whereas, with potassium, there was a lilac flame.
The alkali metals are all of the elements in group 1 of the periodic table.
Group 2 is not called alkali metals, Group 1 is called alkali metals.
Alkali metals are soft, shiny, have a low density, low melting and boiling points and are good conductors of energy.
Because they only need to lose 1 electron, it is very easy for an alkali metal to lose it to end up with a full outer shell, then becoming stable and is therefore, very reactive.
They are used in heat resistant glass and ceramics.
Alkali metals refer to elements in what group of the periodic table?
Group 1
Which of the following are properties of alkali metals?
Soft
Why do alkali metals have similar properties?
Because they all have one electron in their outermost shell. The electron configuration is responsible for how elements react.
Why are alkali metals so reactive?
To become stable
True or false: The more easily an element gets a full outer shell, the less reactive it is.
False
What kind of compounds do alkali metals make?
Ionic compounds
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