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