The Periodic Table

Properties of Elements and Trends

Mendeleev

• The original periodic table was created by Dmitri Mendeleev.

• He organized the table by atomic mass.

• He predicted existence of 3 missing elements (Ga, Sc, Ge)

Modern Periodic Table

• The modern periodic table is organized by atomic number.

Henry Mosely

• Vertical columns called groups or families

• Horizontal rows called periods also represent the shells or energy levels

• The basis of periodic law is repeating patterns.

Major Categories of Elements

• 1) metals 2) non-metals 3) metalloids

• Metals are found to the left of the “staircase”

• Non-metals are found to the right of “staircase”

• Metalloids are found “on” the staircase

Properties of Metals

• Solid at room temperature (except Hg)

• Shiny, Have luster

• Malleable

• Ductile

• Generally have high melting points

• Good conductor of heat and electricity

• Have metallic bonds

Properties of Non-metals

• Can be solid, liquid or gas at room temp• S examples C, S, I2

• L Br2

• G O2, Ne, F2

• Allotropes- different molecular forms of the same element (different properties, too) O2 and O3

• Dull, lack luster• Brittle• Poor conductors

Properties of Metalloids

• Solid at room temperature

• Semi-conductors

• Have varying properties that can be metallic or non-metallic

• Metals tend to lose electrons to form a full valence shell and + ions.

• Non-metals tend to gain electrons to form a full valence shell and – ions.

Groups on the Periodic Table

• In general, elements found within the same group have similar chemical and physical properties.

• This is mainly due to the fact that they have the same number of valence electrons.

Alkali Metals (Group I)

• Metals

• Have one valence electron

• Tend to lose that one electron to become a more stable ion.

• Rarely found in natural state.

Lithium(Li), Sodium(Na), and Potassium(K)

• Three examples of alkali metals

• VERY reactive metals

• Exist as solids at room temperature, but are soft

• Silvery-white or grayish in color

Lithium

Sodium

Potassium

Alkaline Earth Metals (Group II)

• Metals

• Have two valence electrons

• Tend to lose the two electrons to become a more stable ion

Magnesium(Mg), Calcium(Ca) and Strontium(Sr)

• Examples of alkaline earth metals

• Exist as solids at room temperature

• Silvery white or grayish white in color

• Fairly reactive metals

Magnesium

Calcium

Strontium

Halogens Group 17

• Have 7 valence electrons

• Non-metals (F, Cl, Br, I)

• F, Cl (gases), Br (liquid), I (solid)

• Tend to gain one electron to form a more stable ion

• Extremely reactive

Fluorine

Chlorine

Noble Gases Group 18

• Very stable because of filled valence shell.

• Do not react in the presence of other elements (relatively inert)

• Xe can react with Fluorine (more later)

Argon

Xenon

• Used in UV lamps and sun lamps in tanning salons.

Transition Metals

• Also known as “heavy metals”

• Tend to be very dense

• Have varying reactivity

• Have multiple oxidation states (can form more than one ion)

• Have colorful ions (in solution)

Copper

Nickel

Silver

Lanthanide and Actinide Series

• Rare earth metals

• Above 92 they are mostly man-made and are unstable

Periodic Trends• Trends occur in the periodic table in the following areas:

-reactivity-metallic/non-metallic character-atomic radius*-ionization energy* -ionic radius -electronegativity*

Period Trends in Atomic Radius

Atomic radius decreases

Ionization Energy

• The energy required to remove an electron from an atom is known as the FIRST IONIZATION ENERGY.

• To remove a second electron requires what is called the SECOND IONIZATION ENERGY.

Cation Size

• When an electron is lost from an atom, the nucleus now has more pull on the outer energy level making the ion SMALLER.

MINUS ONE ELECTRON

Anion Size

• When an electron is gained the nucleus now has less pull on the outer energy level making the ion LARGER.

PLUS ONE ELECTRON

Electronegativity

• Can be defined as an atom’s ability to attract electrons.

• Expressed in arbitrary units on Table S of your Reference Tables.

• Non-metals tend to have higher electronegativities because they like to gain electrons.

atoms

electrons