Chapter 2.5: Elements

Flashcards from Chapter 2.5 of Chemistry: The Molecular Nature of Matter and Change.

Dmitri Mendeleev

Russian scientist who, in 1871, arranged elements by increasing atomic mass and chemical properties to form the periodic table of elements

Periodic table of elements

Table based on work by Mendeleev, arranged by atomic number

• Arranged in periods (rows) and groups (columns)

  • Each period has a number from 1 to 7; each group has a number from 1 to 18

Group

A column on the periodic table; elements in a group usually have the same outer electron configuration and thus similar chemical behavior

• Numbered from 1 to 18; includes:

  • 1: alkali metals

  • 2: alkaline earth metals

  • 13 to 16: named for first element in group

  • 17: halogens

  • 18: noble gases

• Also called a “family” for elements

Main-group elements

This includes groups 1, 2, and 13 through 18, with predictable outer charges

Transition elements (transition metals)

These include groups 3 through 12

Inner transition elements

Includes the lanthanides and actinides between groups 3 and 4

Alkali metals

The name for group 1, except for hydrogen

• Classified as reactive metals

Alkaline earth metals

The name for group 2

• Classified as reactive metals

Halogens

The name for group 17

• Classified as reactive nonmetals

Noble gases

The name for group 18

• Classified as relatively unreactive nonmetals due to their full valence shells

Element classifications

Can be grouped into three:

• Metals

• Nonmetals

• Metalloids

  • Marked by a staircase line from boron to tellurium (not aluminum)

Metals

Group of elements located in the left and middle portions of the periodic table

• Includes many main-group elements and all transition elements

• Shiny and solid at room temperature

• Can conduct heat and electricity

• Malleable and ductile

Metalloids (semimetals)

Group of elements located along the staircase line of the periodic table

• Includes boron to tellurium, except aluminum

• Shiny and solid, but brittle

• Semiconductors of heat and electricity

• Has properties of both metals and nonmetals

Nonmetals

Group of elements located in the upper-right portion of the periodic table; includes hydrogen as well

• Includes some of the main-group elements

• Gases or dull, brittle solids at room temperature

• Poor conductors

• Not malleable or ductile