Chemistry notes.pdf

atomic theory dalton 5 statements 1. Chemical elements consist of very small particles called atoms 2. All atoms of a specific element are identical but differ from atoms of other elements 3. Chemical compounds are formed by atoms of two or more elements in whole number ratios. 4....

atomic theory dalton 5 statements 1. Chemical elements consist of very small particles called atoms 2. All atoms of a specific element are identical but differ from atoms of other elements 3. Chemical compounds are formed by atoms of two or more elements in whole number ratios. 4. Chemical reactions involve combination, separation or rearrangement of atoms 5. Atoms cannot be created, subdivided or destroyed. describe and label an atom: The building blocks of hydrogen, oxygen and water. Discovered by democritus. Proton: in the nucleus of an atom, positive charge. 1 amu mass. affects atomic number and mass change Neutron: in the nucleus of an atom, neutral charge. 1 amu, affects the mass of an isotope. Electron: in the electron cloud, negative charge. 0 mas. affects the charge of an ion. 4 scientists developed an atom, an experiment they used. Democritus: discovered atoms. No experiment, atoms depicted as random shapes. John Dalton: discovered compounds, mixed two gases and observed their behavior. Depicted as indestructible solid spheres. J.J Thomas: discovered electrons. Beam of particles creating positive charges. Cathode ray tube. Depicted as a circle with positive and negative charged spheres inside Rutherford: discovered the nucleus. Gold foil experiment with flashing screen, alpha particles reacted. Depicted as the model of atom used today. ions and isotopes Ions: Ions gain or lose electrons. Rubidium R+ 37 protons, 36 electrons. Lost one electron Positive Ions: Remove electrons for each positive charge. Negative Ions: Add electrons for each negative charge. Isotopes: contain equal numbers of protons but different numbers of neutrons Nitrogen-15: 7 protons, 8 neutrons, 7 electrons. Number next to the isotope is the mass number Isotopes have different mass and neutrons. periodic trends- deciphering it with the elements -Atomic Radius: Decreases up a group and left to right across a period due to increasing nuclear charge. - Metallic Character: Decreases from left to right and bottom to top, similar to atomic radius. -Metallic Properties: Conductivity. Luster, Hardness, ductility, malleability, high melting point Periodic Law: Properties of elements recur in patterns based on atomic number. Groups and Periods - Groups: Vertical columns; elements exhibit similar chemical properties. - Periods: Horizontal rows; elements show a range of properties. - Group 1: Alkali metals - Group 2: Alkaline earth metals - Group 17: Halogens - Group 18: Noble gases Valence Electrons - Definition: Outermost electrons involved in reactions; represented in electron dot formulas. Ionization Energy - Definition: Energy required to remove an electron; increases up a group and left to right across a period. bohr model vs lewis model Chemical properties Physical properties Chemical changes Physical changes