Metals and Non-Metals
This chapter covers the physical and chemical properties of metals and non-metals, the reactivity series, and extraction of metals, with revision notes, key definitions, solved questions, MCQs and practice problems.
Metals are generally malleable, ductile, sonorous and good conductors of heat and electricity. Non-metals are usually brittle in solid form and poor conductors, except graphite. A few elements, like silicon and arsenic, show properties of both and are called metalloids.
The reactivity series is a list of metals arranged in the order of their decreasing reactivity, from potassium (most reactive) down to gold (least reactive). It is used to predict how metals react with water, acids, and each other in displacement reactions.
Q. Why is sodium kept immersed in kerosene oil?
Sodium is a highly reactive metal that reacts vigorously with oxygen and moisture present in air, catching fire if exposed. Kerosene oil prevents this contact and keeps it safe.
Q. What are the physical properties that make metals useful for making cooking utensils and electrical wires?
Metals used for cooking utensils have high melting points and good thermal conductivity. Metals used for electrical wires have high electrical conductivity and ductility, such as copper and aluminium.
Gold and platinum occur in nature in the free (native) state because they are highly unreactive and do not easily combine with other elements.
Which of the following metals exists in liquid state at room temperature?
Correct answer: (B) Mercury
_______ is the most reactive metal in the reactivity series.
Potassium
All metals react with cold water to produce hydrogen gas.
False — only highly reactive metals like sodium and potassium react vigorously with cold water. Metals like iron react only with steam, and some metals like gold and silver do not react with water at all.
2.4 g of magnesium metal reacts completely with oxygen to form magnesium oxide. If the atomic mass of Mg is 24 and O is 16, calculate the mass of magnesium oxide formed.
2Mg + O2 -> 2MgO. Moles of Mg = 2.4/24 = 0.1 mol, which produces 0.1 mol MgO (molar mass 40 g/mol). Mass of MgO formed = 0.1 x 40 = 4.0 g.