Dans chacune des quatre séries suivantes, classez les...

Dans chacune des quatre séries suivantes, classez les éléments dans l'ordre croissant du rayon de leurs atomes. a) Cs, F, K, N, Li c) Al, In, F, O, Si, S b) $\mathrm{Ba}, \mathrm{Cl}, \mathrm{I}, \mathrm{Sn}, \mathrm{Sr}$ d) $\mathrm{Al}, \mathrm{Ca}, \mathrm{Fr}, \mathrm{Mg}, \mathrm{Rb}, \mathrm{S}$

Dans chacune des quatre séries suivantes, classez les éléments dans l'ordre croissant du rayon de leurs atomes.
a) Cs, F, K, N, Li
c) Al, In, F, O, Si, S
b) $\mathrm{Ba}, \mathrm{Cl}, \mathrm{I}, \mathrm{Sn}, \mathrm{Sr}$
d) $\mathrm{Al}, \mathrm{Ca}, \mathrm{Fr}, \mathrm{Mg}, \mathrm{Rb}, \mathrm{S}$

Key Concepts

Effective Nuclear Charge

The effective nuclear charge is the net positive charge experienced by valence electrons, accounting for both the actual nuclear charge and the shielding effect of inner electrons. This concept explains why atoms in the same period become progressively smaller even if the number of electrons increases, as the pull from the nucleus becomes relatively stronger.

Electron Shielding

Electron shielding is the phenomenon where inner-shell electrons partially block the attraction between the nucleus and the outer-shell electrons. This reduced effective nuclear charge allows for a larger atomic radius, particularly evident in atoms that have more electron shells and are positioned lower in a group.

Periodic Trends

Periodic trends refer to the predictable changes in the properties of elements as you move across periods (rows) or down groups (columns) in the periodic table. For atomic radius, these trends show that atomic size generally decreases across a period due to increasing effective nuclear charge and increases down a group as more electron shells are added.

Atomic Radius

Atomic radius is a measure of the size of an atom, typically defined as the distance from the nucleus to the outermost electrons. It is a fundamental property that can be used to compare different elements and understand their chemical behavior in bonding and interactions.

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