Page 38 - Chemistry_Form_2

Chemistry
for Secondary Schools

The periodic table is a systematic arrangement of elements that helps in
understanding patterns in their physical and chemical properties. Elements in
the same row (period) and the same column (group) exhibit trends in melting
points, boiling points, density, electronegativity, ionisation energy, atomic size,
and reactivity. Recognising these trends is essential for applications in various
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settings, including home settings and industries such as material manufacturing,
energy storage, and healthcare.

Melting point is the temperature at which a solid turns into a liquid. For example,

ice melts into water when exposed to heat, such as on a hot day. On the other
hand, boiling point is the temperature at which a liquid changes into a gas, for
instance water boiling and turning into steam when heated on a stove. Density,
another important property, refers to the mass per unit volume of a substance and
reflects its compactness.

Electronegativity is the tendency of an atom to attract shared electrons in a
chemical bond toward itself. This property plays a crucial role in interactions,
such as those between the ions of salt and water molecules when the salt dissolves

in water. On the other hand, ionisation energy is the energy required to remove an
electron from an atom or ion in its gaseous state. Another fundamental property
is the atomic size or radius, which measures the distance from an atom’s nucleus
to its outermost electron shell.

Reactivity refers to the ability of an atom of a given element to interact chemically
with other substances. For instance, alkali metals (Group 1) are highly reactive
due to their tendency to lose one electron, whereas noble gases (Group VIII)

exhibit minimal reactivity because of their stable electronic configurations.
Understanding these properties and their trends helps to explain the behaviour of
elements in reactions and their industrial applications.

Trends in physical properties across periods

Task 2.5

Use an interactive simulation or any reliable resources to explore the trends in
physical properties across periods of the periodic table. Analyse these trends and
explain their practical applications in real-life scenarios.

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