UNIT TWO CHEM

Group 1 – alkali metals (the most reactive metal elements) (except hydrogen (H)) (s-block)

● 1 valence electron; charge of 1+

● most reactive metals on the periodic table

● very soft, stored in oil to prevent (violent) explosive reaction with water

● called “alkali” because they form high pH “alkaline” solutions after reacting with water

● largest atomic radii on the periodic table

● smallest first ionization energy on the periodic table

● lowest electronegativity and electron affinity on the periodic table

Group 2 - alkaline earth metals (s-block)

● 2 valence electrons, charge of 2+

● Reactive, but not as reactive as Group 1

● Found in Earth’s crust as ores and form alkaline solutions with water, hence the name

Groups 3-12 - transition metals (d-block)

● variable numbers of valence electrons, therefore variable (positive) charges

● high melting and boiling points

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● many have useful properties that are highly valued for industry, the arts, and finances

Group 17 - halogens (p-block)

● 7 valence electrons; charge of 1-

● Most reactive nonmetals on the periodic table

● Range from gas at room temperature (25 oC or 298 K).

● at the top of the group (fluorine) to solid at the bottom (astatine)

● Many are colored at room temperature (F = yellow, Cl = green, Br = red, I = forms purple

vapor)

● All form diatomic molecules except for astatine

● Highest (negative) electron affinity on the periodic table

● Highest electronegativity on the periodic table

Group 18 - noble gases (p-block)

● 8 valence electrons except for helium, He (=2 valence electrons); charge of 0

● Chemically stable and unreactive

● All gases at room temperature (25 oC or 298 K)

● Smallest atomic radii on the periodic table

● Largest first ionization energy on the periodic table

Lanthanides and actinides (f-block)

● All are metals and thus have all the properties of metals

● Many are artificial and/or radioactive