Unit 5: The Periodic Law

Mendeleev

arranged the elements in order of increasing atomic mass, created table in which elements with similar properties were grouped tg, properties of undiscovered elements could be predicted, didn’t apply to some elements

Moseley

arranged atoms according to increasing atomic number, gave us periodic law-physical and chemical properties of the elements are periodic functions of their atomic numbers, produced table in which elements with similar properties fell into same column or group

Group 1

alkali metals, silvery appearance; soft enough to cut w knife, extremely reactive; found as compounds in nature, 1 VE-ns^1

Group 2

alkaline earth metals, harder than alkali metals, less abundant but still found as compounds in Earth’s crust, 2 VE-ns²

Group 13

always combined w other elements in nature, 3 VE-ns² np^1

Group 14

4 VE-ns² np², allotropes-forms of an element in same state of matter, but diff physical and chemical properties

Group 15

properties vary as in group 14, 5 VE-ns² np³

Group 16

act as nonmetals, tend to gain electrons, 6 VE-ns² np^4

Group 17-Halogens

form compounds w metals, reactive nonmetals that tend to gain 1 electron, 7 VE-ns² np^5

Group 18-Noble Gases

Colorless, Unreactive, 8 VE-ns² np^6 (except He w 2)

d-block elements

transition metals, shared conductivity, luster, malleability, atomic size, electronegativity, ionization energy, melting points, and boiling points, multiple oxidation states, tend to lose electrons to become positive

f-block elements

inner transition metals, Lanthanide (4f)- silvery metals, similar reactivity like group 2 : Actinide (5f)- radioactive elements, only 4 exist in nature, rest are synthetic elements created in particle accelerators

atomic radii

one-half the distance between the nuclei of identical atoms that are bonded tg. Decrease L to R (more protons, electrons closer), increase down (+ energy level)

ionization energy

energy required to remove 1 electron from outer shell. Increase L to R (more protons, more force), decrease down (more distance from nucleus, less force)

electron affinity

difference in energy when an electron is added to a neutral atom, most release energy and some require energy to gain electron. Increase L to R (more + charge, more force, more EA), decrease down (more radius, more distance, less force, less EA)

electronegativity

ability of an atom in a compound to attract electrons from another atom in the compound. Increase L to R (more + charge, greater attraction force), decrease down (more energy level, more radius, more distance, less force). Fluorine is greatest

ionic radii

radii of the most common ions of the elements. positive-cations, negative-anions. Cation-decrease L to R, Anion-increase L to R, both increase down (more # of energy levels)

valence electrons

electrons available to be lost, gained, or shared in the formation of chemical compounds

nonmetals _ electrons and become _ charged

gain; negatively

Anions would have _ electron affinity, _ ionization energy

high; high

Cations would have _ electron affinity, _ ionization energy

low; low

Relationship between distance from nucleus and attractive force

indirect - increased distance, decreased force

Relationship between effective nuclear charge and attractive force

direct- increased positive charge, increased force