Modern Periodic Table
The Modern Periodic Table
• The Periodic Table is a listing of all the known elements.
• The elements are organized by:
• Atomic number
• Chemical Properties
Groups and Periods
• Group( or Family): a vertical column. Elements in groups have similar chemical properties.
• Period: a horizontal row.
Groups and Periods are numbered.
• There are 7 periods.
• There are 18 numbered columns.
Periods
• The periods (rows) of the periodic table indicate the highest energy level occupied by one or more electrons.
Valence Electrons
• The electrons the occupy the highest energy level of an atom.
• Valence electrons play a key role in the chemical properties of an element.
“A” Groups (Old System)
• The “A” groups are numbered 18.
• The number of the “A” groups correspond to the number of valence electrons.
Group 1- Alkali Metals
• 1 valence electron (ns1)
• Form a 1+ ion.
• Note: Hydrogen, a nonmetal, is located in the first column because it has one valence electron.
Group 1- Alkali Metals
Lithium
Sodium Potassium Rubidium Cesium Francium
The word alkali comes from Arabic. It can be roughly translated into 'dissolved ashes.' When one dissolves soda ash in water, a basic solution is formed. This is likely where the term alkali comes from when referring to a basic substance.
Alkali metals, after reacting with water, form basic solutions (take sodium metal for example - when it reacts with water, it forms sodium hydroxide, a strong base). This connection is
where the name alkali comes from in reference to the group 1A
elements
Reactivity of Alkali Metals
• Increases from top to bottom of the group.
• Which is more reactive Cesium or Sodium?
4M+O2⟶2M2O;
M2O+H2O⟶2MOH.
Note:
• Sodium and Potassium are stored in oil to keep them from reacting with oxygen and water in the air.
• Cesium is stored in glass tubes of argon gas( an inert gas).
Group 2- Alkali Earth Metals
Beryllium Magnesium Calcium Strontium Barium Radium
Apparently a scientist got those metals by electrolysis of their oxidized forms, which are found naturally in the earth.
Group 2- Alkali Earth Metals
• Have 2 valence electrons.
• Form 2+ ions.
Group 2- Alkali Earth Metals Reactions with Water
• Be does not react with water.
• Mg reacts with hot water.
• Ca, Sr, Ba react easily with cold water.
• Which way along the group does reactivity increase?
Notes:
• There is Mg in chrolophyll C55H72O5N4Mg
• Calcium is in your bones, chalk, limestone, toothpaste, pearl (all as calcium carbonate).
