Chemistry - Chapter 6 - The Periodic Table and Periodic Law

Johann Dobereiner

first classified elements into sections called “triads”. Model of Triads

John Newlands

classified elements into octaves, noting that every eighth element had similar properties

Mendelev

created the periodic table, arranging elements by increasing atomic mass and predicted 3 missing elements later found, Sc, Ga, Ge

Periodic Law

when elements are arranged by increasing atomic number and the physical/chemical properties show a pattern

Properties of elements in the same groups

they have = valence electrons

Properties of metals

Metals tend to be shiny, malleable, ductile, and good conductors of heat and electricity. Usually solid @ room temperature

Properties of nonmetals

Nonmetals are generally dull, brittle, and poor conductors of heat and electricity. They tend to gain electrons in chemical reactions. Usually all 3 states of matter at room temperature: solid, liquid, or gas.

Properties of metaloids

Metalloids exhibit mixed properties of metals and nonmetals, often being intermediate conductors of electricity. They can be shiny or dull and are usually brittle

Alkali

metals are highly reactive, soft, and typically have one electron in their outermost shell. They react with water and oxygen and form bases and aren’t found in nature

Alkaline

earth metals are elements in group 2 of the periodic table, known for their reactivity and aren’t found in nature

Halogens

are highly reactive nonmetals in group 17 of the periodic table, known for forming salts with alkali metals. They are also the most electronegative

Noble gasses

are colorless, odorless gases in group 18 of the periodic table, known for their lack of reactivity due to having a full valence shell.

Transition

metals are elements in groups 3 to 12 of the periodic table, have high luster and form variable oxidation states and colored compounds.

P-block

are groups 13 to 18 of the periodic table, containing a mix of metals, nonmetals, and metalloids, known for their diverse chemical properties.

Coulomb’s Law

the greater the distance between the electrons and nucleus, the lower the force, however the more protons there are, the greater the force is. Can be used to explain atomic radii, and other periodic trends.

Group and Period Trends

Group is vertical

Period is horizontal

trends include: atomic radii, electronegativity, ionization energy, electron affinity, and Zeff

Atomic Radii

the distance from the nucleus to the electrons that is measured in PM and decreases across, but increases down

Electronegativity

The energy needed for an atom to attract an electron from itself when combined with another element, increases across, decreases down

Ionization Energy

The amount of energy needed to take out an electron from the valence shell. Increases across, decreases down

Electron Affinity

The energy released when electrons are gained, increases across decreases down

Ionic Size

Increases down, decreases across. cations lose and and get smaller, anions gain and become larger

Shielding

The core electrons protecting the outermost electrons

Zeff

Z-S=Zeff

Z= atomic number

S= total core electrons (all electrons excluding valence)

The higher the Zeff, the closer to the nucleus they are