Notes: Chemical Periodicity

Dmitiri Mendeleev ( ) The first to relate the known elements in an ordered arrangement according to their chemical properties. (mass)

Mendeleev’s Periodic Table Spaces left for “missing” elements Were later discovered Mendeleev was able to predict trends using his periodic table

Henry Moseley ( ) Was the first to determine the atomic number of all the known elements and used them to order the elements.

The Modern Periodic Table Horizontal rows are called periods. Vertical columns are called groups or families.

To number your periodic table

Blocks: s, p, d, f

Number/color your periodic table

Noble Gases Elements in which the outermost s and p sublevels are filled. (group/family 8A) Also called inert gases because they generally do not react with any other element.

Noble Gasses

Representative Elements Elements in which the outermost s or p sublevels are only partially filled. The group numbers equal the number of electrons in the outermost occupied energy level.

Metals Left side of periodic table Conduct heat and electricity Reflect light Solids at room temperature (one exception)

Metals

Properties of Metals Ductile Malleable  stretched/pulled out (into wire)  pliable

Transition Metals D block

Inner Transition Metals F block

Metalloids Along stair-step line Behave like a metal in some conditions, nonmetal in others

Nonmetals Upper-right Great variation in properties Most gases, some solids, one liquid at room temperature

Properties of nonmetals Poor conductors of heat/electricity Brittle

Trends in Atomic Size Group trends -atomic size generally increases as we move down a group of the periodic table. Periodic trends - atomic size generally decreases as we move from left to right across a period.

Electronegativity Tendency for an atom to attract electrons to itself when it is chemically combined with another element.

Electronegativity Increases as you go up in a group. Decreases as you go down. Increases as you go to the right in a period. Decreases as you go to the left.

Valence Electrons Electrons an element contains in its outermost energy level

Valence Electrons Elements with fewer than 4 tend to lose electrons

Valence Electrons Elements with more than 4 tend to gain electrons

Group Names and Properties

Alkali Metals Group 1A (except for H) They have low densities, low melting points and good electrical conductivity (extremely reactive). 1 electron in outer energy level (s orbital)

Alkaline Earth Metals Group 2A Less reactive than Group 1A, but still very reactive. 2 electrons in outer energy level

Aluminum Group Includes the elements in Group 3A. Includes metals and nonmetals.

Carbon Group Includes the elements in Group 4A. Carbon is the main component of organic compounds. Silicon is the second most abundant element on earth.

Nitrogen Group Includes the elements in group 5A.

Oxygen Group Includes the elements in Group 6A. Oxygen is the most abundant element on earth.

Halogens From the Greek “salt-generating” Group 7A 7 electrons in outer energy level Elements end in “–ine” Only group which contains all three states of matter EXTREMELY reactive

Halogens and Hydrogen Nonmetals that often combine with elements from Groups 1A and 2A.

Halogens and Hydrogen Hydrogen is in a group by itself. It is usually put in a group with the elements from Group 1A even though it is not a metal.

Halogens and Hydrogen Hydrogen reacts easily with halogens.