chem ch 6

Atomic Radius

Half the distance between two nuclei of same element.

Atomic Radius Trend (Across a Period)

Decreases left to right due to nuclear charge increase.

Atomic Radius Trend (Down a Group)

Increases due to more occupied energy levels.

why Decrease Reason Across Period

Core electrons constant; nuclear charge increases.

why increase Reason Down a Group

More energy levels reduce nuclear pull on electrons.

First Ionization Energy

Energy needed to remove the first valence electron.

Ionization Energy Trend (Across a Period)

Increases due to higher nuclear charge charge pulling valence electrons closer.

Ionization Energy Trend (Down a Group)

Decreases as electrons are farther from nucleus.

Trends Explanation

Core electrons constant increase nuclear attraction across period.

Electronegativity

The ability of an atom to attract bonded electrons to itself.

Electronegativity Trend (Across a Period)

Increases as nuclear charge attracts electrons more strongly.

Electronegativity Trend (Down a Group)

Decreases as valence electrons are farther from nucleus.

Second Ionization Energy

Energy required to remove second electron after first.

Coulomb's Law

Force depends on charges and distance: F ∝ q1*q2/d².

High Second Ionization Energy (Sodium)

Second electron is in core level, needing more energy.

Cesium Ionization Energy

Low ionization energy allows easy electron loss.

Fluorine Electronegativity

High electronegativity allows easy electron gain.

Ionic Bond (Cesium and Fluorine)

Strong bond formed due to electron transfer.

Nuclear Charge

Total # of protons in the nucleus.

Valence Electrons

Electrons in the outermost shell of an atom.

Mendeleev

Russian chemist who developed a periodic table of the chemical elements and predicted the discovery of several new elements (1834-1907)

Moseley

Arranged the periodic table by atomic number instead of mass.

Seaborg

Arranged Periodic Table by pulling out lanthanides and actinides, inner transition metal section

Periodic Law

the physical and chemical properties of the elements are periodic functions of their atomic numbers