Atomic Theory

• 1897 - J.J. Thomson discovered the electron

• 1911 - Rutherford discovered the nucleus

• 1913 – Bohr put electrons into circular pathways called orbits around the nucleus of the atom

• 1920’s – Schrodinger put electrons into electron clouds

• 1932 - Chadwick discovered the neutron

Types of CompoundsCovalent Compounds

• electrons are shared among atoms

• have lower melting points

• do not conduct electricity when dissolved in water

Ionic Compounds

• electrons are transferred among atoms

• most are crystalline solids

• have high melting points

• are hard and brittle

• conduct electricity when melted or dissolved in water

Acids and BasesAcids

• taste sour

• pH ranges from 0 to 6.9

• change the color of litmus paper from blue to red

• react with metals

• produce H+1 ions when placed in water

Bases

• taste bitter

• feel slippery

• pH ranges from 7.1 to 14

• change the color of litmus paper from red to blue

• produce OH-1 ions when placed in water

The Periodic TableGroup 1 Elements – Alkali Metals

• Alkali metals are dull, silvery colored metals that are extremely soft. They are so soft that they can be cut with a knife.

• They are the most reactive metals.

Group 2 Elements – Alkaline Earth Metals

• Alkaline earth metals are shiny, silvery-white colored metals. They are much harder than the alkali metals (group 1).

• They are reactive, but not nearly as reactive as the alkali metals (group 1).

Group 17 Elements – Halogens

• They vary in their physical appearance, but the are most reactive of the nonmetals.

Group 18 Elements – Noble Gases

• The noble gases are all gases at room temperature.

• They are also the most stable, least reactive, group of elements on the periodic table.

Periodic TrendsAtomic Radius

• decreases going across the periodic table

• For example, in period 2, lithium (Li) is the biggest atom and neon (Ne) is the smallest.

Atomic Radius

• increases going down a group

• For example, in group 1, hydrogen (H) is the smallest atom and francium (Fr) is the biggest.

Ionization Energy

• increases going across the periodic table

• For example, in period 2, lithium (Li) has the smallest ionization energy and neon (Ne) has the biggest.

Ionization Energy

• decreases going down a group

• For example, in group 1, hydrogen (H) has the largest ionization energy and francium (Fr) has the smallest.

Electronegativity

• Increases going across the periodic table

• Group 18 elements (noble gases) have ZERO electronegativity

• For example, in period 2, lithium (Li) has the lowest electronegativity and fluorine (F) has the largest.

Electronegativity• decreases going down a group

• Again, group 18 elements (noble gases) have ZERO electronegativity

• For example, in group 1, hydrogen (H) has the largest electronegativity and francium (Fr) has the smallest.

Nuclear Chemistry

Alpha Radiation

• Alpha particles are fast moving helium atoms.

• Due to their large mass, they are stopped by just a few inches of air or a piece of paper.

Beta Radiation• Beta particles are fast

moving electrons. • Since electrons are

much lighter than helium atoms, they are able to travel farther than alpha particles.

• Beta particles can be stopped by heavy clothing, aluminum foil or wood.

Gamma Rays• Gamma rays are

photons, just like light, except they are higher in energy.

• Gamma rays are very similar to x-rays.

• They can be stopped by a few inches of concrete or lead