Chapter 5: The Periodic Table 5.1 Organizing the elements 5.2 The Modern Periodic Table 5.3 Representative groups

Organization of the Elements Section 5.1 Organization of the Elements

The Search for Order (Reasons for order) Brings order to seemingly unrelated facts Helped chemists predict the existence of elements that weren’t discovered yet Groups elements according to their chemical and physical properties

Mendeleev’s Periodic Table Strategy for organization: What did he look at? chemical properties physical properties atomic mass density color melting point valence

Mendeleev’s Proposal Elements arranged in rows based on increasing mass. Elements with similar properties are in same column. Chart was a Periodic Table/ DEF. arrangement of elements in columns based on a set of properties that repeat.

Mendeleev’s Prediction Table incomplete– elements not yet discovered Left spaces in table for undiscovered elements

Evidence Supporting Mendeleev’s Table Close match between Mendeleev’s predictions and the actual properties of new elements showed how useful table was. Ex. Discovery of: Aluminum, Gallium, Scandium, and Germanium

The Modern Periodic Table Section 5.2 The Modern Periodic Table

Repeating patterns Elements in same column are related because properties repeat in regular intervals

The Modern Periodic Table Listed in order of increasing number of protons Properties of the elements repeat. Periodic Law- when the elements are arranged in order of increasing number of protons, the properties tend to repeat in a pattern

Columns in the Periodic Table -vertical classification or groupings -often referred to as families or groups -each column is numbered 1-18 or 1A through 8A -elements within the same family have similar properties

Rows in the Periodic Table -horizontal classification or groupings -each row is called a period -elements in a period are not alike in properties, properties change greatly across a given row -the first element in a period is a very active metal -the last element in most periods is a noble gas -only seven periods

Element Key Important information about an element is given in each square of the periodic table: its atomic number chemical symbol element name atomic mass 6 C Carbon 12.01 For example: Carbon has an atomic number of 6 (or has 6 protons), an atomic mass of 12.01 and a symbol of C

Atomic Mass Two isotopes of copper Makes the average 63.56 amu

Metals Majority of elements Luster – shiny. Ductile – drawn into thin wires. Malleable – hammered into sheets. Conductors of heat and electricity. Include transition metals – “bridge” between elements on left and right of table

Non-Metals Properties are generally opposite of metals Poor conductors of heat and electricity Low boiling points Many are gases at room temperature Solid, non-metals are brittle (break easily) Chemical properties vary

Metalloids Have properties similar to metals and non-metals Can conduct heat and electricity like metals but not as good

Variation Across a Period: Left to Right Physical and Chemical properties Atomic size decreases Metallic properties decrease Ability to lose an electron decreases Ability to gain electrons increases Ion (charged atom) pattern is seen 1 2 3 4 3 2 1 0

Representative Groups Section 5.3 Representative Groups

Valence electrons The electrons in the outermost energy level Responsible for most of the chemical properties When two atoms interact, the outside electrons are the ones affected Elements in a group have similar properties because they have same number of valence electrons

Ten major families: 1. alkali metals 2. alkaline earth metals 3 Ten major families: 1. alkali metals 2. alkaline earth metals 3. transition elements 4. boron family 5. carbon family 6. nitrogen family 7. oxygen family 8. halogen family 9. noble gases 10. rare earth metals

Alkali Metals - one electron in their outermost shell or one valence electron - soft, silver-white, shiny metals - bond readily with other substances - never found uncombined in nature - samples must be stored in oil to keep them from combining with water or oxygen - most reactive metals - Reactivity increases down a group

Alkaline Earth Metals - two valence electrons - lose 2 electrons when combined with other substances - never found uncombined in nature - not quite as reactive as the alkali metals - often mixed with other metals, such as aluminum, to form alloys of strong yet light in weight metals

Alkaline Earth Metals cont… Magnesium Used to make steel (lighter metal without sacrificing strength) Key role in photosynthesis (found in chlorophyll) Calcium Found in bones and teeth Chalk, limestone, coral, pearls, toothpaste, plaster

5 B Boron 10.81 Boron Family -have 3 valance electrons Boron hard and brittle never found uncombined in nature found in borax used to make heat resistant glass (used in laboratories) 5 B Boron 10.81

Boron Family 13 Al Aluminum 26.98 Aluminum most abundant metal in earth’s crust found in a mineral called bauxite extremely important metal for industry, light, strong and slow to corrode 13 Al Aluminum 26.98

Carbon Family Have 4 valance electrons Can either gain 4 electrons or lose 4 electrons Most compounds in the body contain carbon Silicon 2nd most abundant element in Earth’s crust Silicon used to tip saw blades

Nitrogen Family Have 5 valence electrons Tend to gain 3 electrons Nitrogen and Phosphorous used in fertilizers Phosphorous used in matches

Oxygen Family Have 6 valence electrons Tend to gain 2 electrons Oxygen most abundant element Sulfur used in fertilizers Oxygen needed to for digestion

Halogen Family -have 7 valence electrons -most active nonmetals -never found free in nature -react with the alkali metals quite easily -when halogens react with metals they form compounds called salts -Fluorine is the most active halogen

Halogens cont… Fluorine compounds used in toothpaste Chlorine used to kill bacteria Iodine keeps thyroid gland working properly

The Noble Gases (Inert Gases) -normally non-reactive -also called inert -all elements in this family are gases -outermost electron shell is full -found in small amounts in the earth’s atmosphere (less than 1%)

Other Areas Transition Metals Rare Earth Elements Lanthanide series Actinide Series