Group 1 - chemical reactions with water
The smallest part of an element that can exist. of The first vertical column of elements in the periodic table, starting with lithium and ending with francium. Also called the alkali metals. A substance made of one type of atom only. all have one Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. in their outer shell. This means that the alkali metals all have similar A description of how a substance reacts with other substances. For example, flammability, pH, reaction with acid, etc..
When a group 1 element takes part in a reaction, its atoms each lose one electron. This forms positively charged Electrically charged particle, formed when an atom or molecule gains or loses electrons.. The ions have a stable arrangement of electrons, with a complete outer shell.
Reactions with water
The alkali metals react with water to produce a metal hydroxide and hydrogen. For example, sodium reacts with water:
sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Sodium hydroxide is an A base which is soluble in water.. It is a A substance that reacts with an acid to neutralise it and produce a salt. that When a substance breaks up and mixes completely with a solvent to produce a solution. in water to form an Having a pH greater than 7. Mixture formed by a solute and a solvent.. This solution:
- has a Scale of acidity or alkalinity. A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline. greater than 7
- turns A chemical solution that produces many different colour changes corresponding to different pH levels. solution blue or purple
Question
Write the word equation and balanced symbol equation for the reaction of potassium with water.
potassium + water → potassium hydroxide + hydrogen
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)
Reactions compared
The table shows observations when lithium, sodium and potassium are added to water. Notice that the A measure of how vigorously a substance will react. The more reactive it is, the greater its reactivity and the more vigorous its reactions will be. of these metals increases going down the group. This pattern is seen with all reactions of group 1 elements. For example, the reaction of caesium with chlorine is more vigorous than the reaction of potassium with chlorine.
| Element | Observation when added to water |
| Lithium, Li | Fizzes steadily; slowly becomes smaller until it disappears |
| Sodium, Na | Fizzes rapidly; melts to form a ball; quickly becomes smaller until it disappears |
| Potassium, K | Burns violently with sparks and a lilac flame; quickly melts to form a ball; disappears rapidly, often with a small explosion |
| Element | Lithium, Li |
|---|---|
| Observation when added to water | Fizzes steadily; slowly becomes smaller until it disappears |
| Element | Sodium, Na |
|---|---|
| Observation when added to water | Fizzes rapidly; melts to form a ball; quickly becomes smaller until it disappears |
| Element | Potassium, K |
|---|---|
| Observation when added to water | Burns violently with sparks and a lilac flame; quickly melts to form a ball; disappears rapidly, often with a small explosion |
Question
Rubidium is placed below potassium in group 1. Predict what is seen when rubidium is added to water.
Rubidium should melt very quickly. It should burn very violently, and disappear almost instantly with an explosion.