Atomic Theory J.J. Thomson discovered the electron 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 Chadwick discovered the neutron

Types of Compounds Covalent 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 Bases Acids 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 Table Group 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 Trends Atomic 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