Elements in Group 1

4.4

Elements in Group 1

Also known as alkali metals, except for hydrogen.
Can be found in the leftmost column of the periodic table.

This image shows a simplified periodic table of elements. The table is color-coded with elements in the first and eighteenth groups highlighted. The first group elements (H, Li, Na, K, Rb, Cs, Fr) are in purple, while the eighteenth group elements (He, Ne, Ar, Kr, Xe, Rn, Og) are in pink. The rest of the elements are represented by empty white squares. The background of the table is light blue.

Physical Properties of Group 1 Elements

These metals are soft.
Good conductors of heat and electricity.

Changes in Physical Properties of Elements When Going Down Group 1
Element	As Going Down the Group
Li	The atomic radius increases. Density increases. The melting point decreases. Electeopositivity also increase The attractive force between the nucleus and the single electron decreases as the radius increases.
Na
K

Chemical Properties of Group 1 Elements

React with Water to Produce Hydrogen Gas and Alkaline Solution

Element	Reaction with Water
Li	\(2Li(s) + 2H_2O(l) \rightarrow 2LiOH(aq) + H_2(g)\)
Na	\(2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)\)
K	\(2K(s) + 2H_2O(l) \rightarrow 2KOH(aq) + H_2(g)\)

React with Oxygen to Produce Metal Oxide

Element	Reaction with Oxygen
Li	\(4Li(s) + O_2(g) \rightarrow 2Li_2O(s)\)
Na	\(4Na(s) + O_2(g) \rightarrow 2Na_2O(s)\)
K	\(4K(s) + O_2(g) \rightarrow 2K_2O(s)\)

React with Halogen to Produce Metal Halide

Element	Reaction with Chlorine
Li	\(2Li(s) + Cl_2(g) \rightarrow 2LiCl(s)\)
Na	\(2Na(s) + Cl_2(g) \rightarrow 2NaCl(s)\)
K	\(2K(s) + Cl_2(g) \rightarrow 2KCl(s)\)

Reactivity

The elements are very reactive as going down the group.
The elements will tend to donate an electron and become positive ions.
The donation of an electron is to make sure it can attain a stable duplet or octet electron arrangement.
The attractive force between the nucleus and the valence electron is weak, thus making it easier to be donated or released.
As going down the group, the atomic radius of the elements increases, causing the force between the nucleus and the electron to be weaker.

Element

As Going Down the Group

\(\Downarrow\)

The atomic radius of the elements increases

\(\downarrow\)

The attractive force between the nucleus and the valence electron becomes weaker

\(\downarrow\)

Easier to release the valence electron

\(\downarrow\)

The reactivity of the reaction increases

Physical and Chemical Properties of Other Elements in Group 1 (Rubidium, Caesium, dan Fransium)

Soft metals with shiny surfaces and have low melting point and boiling point.
Rubidium and caesium are metals that are very reactive and burn easily.
Rubidium and caesium are usually combined with other elements.
They are difficult to be isolated chemically.
Francium element is an unstable radioactive isotope with a short half-life.
All three elements are very reactive with water and oxygen.