Periodic Properties and Variations of Properties - Physical and Chemical

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The Modern Periodic Law was proposed by Moseley. It states that 'The physical and chemical properties of the elements are periodic functions of their atomic numbers.' This means that when elements are…

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Atomic radius is the distance from the center of the nucleus to the outermost shell (valence shell) of electrons. Units: Angstrom (Å) where 1Å = 10⁻⁸ cm = 10⁻¹⁰ m, or picometers (pm) where 1 pm = 10⁻¹…

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Down a group: Atomic radius INCREASES because new shells are added, making the atom larger despite increased nuclear charge. Across a period: Atomic radius DECREASES because nuclear charge increases …

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Ionization energy is the minimum amount of energy required to remove the most loosely bound electron from an isolated gaseous atom to form a cation. Equation: M(g) + Energy (IE) → M⁺(g) + e⁻ Units: …

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Down a group: Ionization energy DECREASES because atomic size increases and valence electrons become farther from nucleus, making them easier to remove. Across a period: Ionization energy INCREASES b…

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Highest: Helium (He) - due to its small size and complete outer shell Lowest: Cesium (Cs) - due to its large size and single valence electron in the outermost shell that is far from the nucleus…

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Electron affinity is the energy released when an electron is added to the outermost shell of an isolated gaseous atom to form a gaseous anion. Equation: X(g) + e⁻ → X⁻(g) + Energy (E.A.) Units: kJ m…

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Although fluorine is more electronegative, chlorine has higher electron affinity than fluorine. This is because fluorine has a very small atomic size, leading to high electron density. When an electro…