Group 1 is the first group of the periodic table. This group is located on the first column of the periodic table. Like other groups, group 1 is essential. All the members of group 1 show similar properties but they all are different from other groups. Let's find out the properties of group 1.
What is Group 1?
Group 1 (also known as alkali metals) can be found on the far left of the periodic table. The members of group 1 have similar properties and that is why they are placed in group 1.
Group 1 elements have different properties than other groups and this makes them unique. To understand group 1 properly, we need to check its physical and chemical properties.
Physical Properties
All the members of all group 1 are solid metals. However, all the elements of group one have low melting and boiling points due to low intermolecular forces of attraction. To overcome these forces of attraction, a low amount of energy is required and that is why they have low melting and boiling points. Another physical property is density. Densities of group 1 members are low too. Although, these conditions don't support that these metals are solid yet they are solids.
Another physical property of group 1 is that they are soft. Elements of group 1 are so soft that they can be easily cut using a knife.
Trends of Group 1
As you move down the group, the melting and boiling point of elements decreases. For example, melting point of lithium is 180ºC, however, the melting point of caesium is 28ºC. This is because as the number of electrons increases, the shell increases and the valance electron gets far. The force of attraction between the nucleus and valance electron becomes low as you move down the group and that is why they have low melting and boiling points. In addition, densities also decrease as you move down the group. Elements of group 1 also become softer as we move down the group.
Chemical Properties
Group 1 have more chemical properties than physical properties. The first chemical property is that group 1 elements will always form positive ions. For example lithium, lithium has an extra electron in its valance shell. To make itself stable, lithium needs to donate that extra electron. When it donates an electron, the force of attraction balance breaks. Number of electrons is lower than the number of protons and since protons are positively charged particles, the whole element will also become a positively charged particle, in short, an ion. Since lithium will donate just a single electron, it will have a +1 charge and this goes for all elements in group one. Therefore, group 1 elements will always have a +1 charge on them.
Reaction with Water
Due to the availability of extra electrons, group 1 elements are readily available for reaction. Group 1 elements react with water to form hydroxide. Group 1 elements are alkali elements. When alkali is dissolved in water, they form hydroxide.
For example, sodium is a group one element. Sodium is available for reaction to form sodium hydroxide compounds. Below is the chemical reaction of sodium with water:
Sodium + water → sodium hydroxide + hydrogen
And this is the chemical equation of the above reaction:
2Na + 2H2O →2NaOH + H2
The reaction is violent in nature. When sodium reacts with water, a lot of heat is liberated. In fact, there is a good chance of fire to start. Another observation would be the bubbles in the water. Those bubbles will be of hydrogen gas that is liberated as sodium reacts with water. The resultant chemical produced will be an alkaline solution. This means that the pH of the solution will be greater than 7.
This goes for all the members of group 1. They will react with water to form the hydroxide, creating an alkaline solution that will shoot the pH above 7 and will liberate hydrogen. As a matter of fact, the stoichiometric ratios will be the same as well. Just for the sake of discussion, below is the chemical reaction of lithium with water.
2Na + 2H2O → 2NaOH + H2
Both reactions are almost the same, just the difference is that we used sodium previously and this time, we used sodium.
Reaction with Oxygen
Group 1 elements are also available for reaction with oxygen. When group 1 elements react with oxygen, they will form oxide. Oxygen requires two electrons to complete its valance shell and that is why two atoms of the group 1 element are required to react with one oxygen.
For example, potassium reacts with oxygen to form potassium oxide. Below is its chemical reaction:
4K + O2 → 2K2O
In the above reaction, there are two oxygen atoms. Each oxygen atom requires two potassium atoms because potassium is willing to donate one electron. Oxygen needs two electrons. Hence, oxygen will take the single electron from each potassium.
Furthermore, these metal oxides are bases. It means they are alkaline in nature increasing the pH value. Not to mention that all members of group 1 will undergo the oxidation reaction.
Reaction with Chlorine
Last but not least, group 1 elements also react with chlorine to form chloride compounds. One of the biggest examples of chloride compounds is sodium chloride. It is the same compound that you use in cooking, it's another name is table salt.
Chlorine requires only one electron to complete its valance shell and group 1 elements are willing to donate their single electron in their valance shell to become stable. Below is the chemical reaction of sodium with chlorine.
Na + Cl → NaCl
Every group 1 element will undergo a chlorine reaction like above.
Trend Down the Group
As you move down the group, reactivity increases. This is because the number of shells is increasing down the group. It means that the valance electron is moving far from the nucleus. The force between the nucleus and the last electron will get weaker. This will result in weak intermolecular forces and as the forces will decrease, the easier it will get for the electron to eject from the shell. In other words, the element can easily donate its last electron due to weak intermolecular forces. That is why reactivity increases down the group. All the above reactions, oxidation reaction, reaction with water, and chlorination reaction, will get more vigorous as you move down the group.
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Lithium is used in place of Fluorine
Hi Madan. You’re right to point that out – thanks very much for your comment!
amazing side
It’s very educative,I learnt alot thanks ❤️
Was very educative and help. Gave me a broader understanding of the topic