Nearly three fourth elements shown in the periodic table are called metals. Metals show remarkable properties. Mostly metals occur in earth crust in the form of their oxides, hydroxides, carbonates and sulphides, etc. Metals have a tendency to lose electrons and form cations. Usually they form ionic bonds with other elements.
Most of the elements present in the first and second group of the periodic table react vigorously with cold water producing their respective hydroxides and hydrogen gas.
Interesting Information: If two pieces of uncoated metal touch in space, they become permanently stuck together. It does not happen on Earth because the atmosphere puts a thin layer of oxide between the surfaces which acts as a barrier preventing adhesion.
Magnesium, however, reacts with cold water slowly giving magnesium hydroxide and hydrogen gas.
The more reactive the metal, the more readily it reacts with steam. Reactive metals like lithium, sodium, potassium and calcium react violently with steam and the reaction can be dangerous. Beryllium and aluminum react with steam at high temperatures (around 700°C) to give their respective oxides and hydrogen.
Metals react with oxygen to give metal oxides. The ease of reaction and the type of oxide which is formed, depends upon the reactivity of metals and the conditions used. Sodium burns in air with yellow flame producing both sodium oxide and sodium peroxide.
Magnesium, calcium, strontium and barium burn in oxygen with colour of the flame characteristic to each metal giving their respective oxides.
| Metal | Colour of flame |
|---|---|
| Mg | Intense white flame |
| Ca | White flame with a tinge of red |
| Sr | Crimson flame |
| Ba | A pale green flame |
Figure 19.3: Strontium flame & Figure 19.4: Barium flame (characteristic colors)
The more reactive the metal the more vigorous is its reaction with dilute acids. Sodium and potassium are very dangerous and react violently with dilute acids giving their respective salts and hydrogen gas. All group 2 elements react with dilute acids giving their salts, and hydrogen gas. The reaction generally becomes more vigorous as we move down the group.
Based on their reactions with water and acids, the metals can be arranged in decreasing order of their reactivities. Such an arrangement is called the reactivity series of metals. According to this reactivity series, calcium and metals above it react with cold water to give metal hydroxides and hydrogen gas. The metals below calcium do not react with cold water, instead they react with steam to give metal oxides and hydrogen gas.
Only metals above hydrogen will be able to liberate H₂ upon reacting with dilute acids. Unreactive metals below hydrogen do not react with dilute acids. The more reactive the metal, the more vigorous its reaction will be with dilute acids. Similarly reactive metals, like potassium and sodium, react with oxygen easily whereas the less reactive metals like silver, copper and iron react with oxygen much more slowly.
The metals at the top of the series are powerful reducing agents since they are easily oxidized. However, the reducing ability of metals decreases going down the series.
📌 19.4 Quick Check (solutions)
| Session | Learning objectives | Activities & resources | Assessment |
|---|---|---|---|
| Day 1 | Introduction to metals; occurrence; reaction with cold water (Na, K, Mg) | Demonstrate equations; discuss space adhesion fact; compare reactivity | Write equations: K + H₂O, Mg + H₂O (cold) |
| Day 2 | Reaction with steam (Be, Al, Mg, Zn, Fe); conditions and products | Explain why some metals need steam not cold water; write equations | Quick check 19.4 Q2; balance Al + steam |
| Day 3 | Reaction with oxygen; flame colors (Na, Mg, Ca, Sr, Ba); oxides/peroxides | Show flame color chart; discuss sodium peroxide formation | Recall flame colors; write Na + O₂ reactions |
| Day 4 | Reaction with dilute acids; trend in group 2; metals above/below hydrogen | Demonstrate Mg + HCl; discuss safety for Na/K; relate to reactivity series | Predict products: Ca + H₂SO₄, Cu + HCl |
| Day 5 | Reactivity series; reducing agent trend; displacement reaction (Zn + CuSO₄) | Arrange metals in order; explain displacement with example | Quick check 19.4 Q1; displacement prediction |
| Day 6 | Review & integrated quiz | Solve 10 MCQs; discuss real-life applications | MCQ quiz & key analysis |
⏱️ Each session ~40-45 min. Use @everexams.com quiz for instant feedback.
Click on option — correct turns green, wrong turns red. Use submit to see score & key.