CHAPTER 2 AP CHEMISTRY

LAWS LAW OF CONSERVATION OF MASS Mass cannot be created nor destroyed in a normal chemical reaction LAW OF DEFINITE PROPORTIONS Compounds always contain the same elements in the same proportions by mass LAW OF MULTIPLE PROPORTIONS Masses of one element combines with a fixed mass of a second element

ATOMS John Dalton Each element composed of atoms Atoms of a given element are identical; Atoms of different elements are different Chemical compounds are formed when atoms combine with each other. In a given compound, the relative numbers and kind of atoms are the same

COMPONENTS OF A ATOM ELECTRONS Thomson found a charge to mass ratio of an electron to be : 1.76 x 10 8 C/g Discovered the electron in 1897 Used the cathode ray, Millikan’s oil drop experiment determined the electron mass to be 9.11 x kg RADIATION Becquerel discovered radioactivity Three type of radiation Gamma (γ) rays are high-energy “light” Beta (β) rays are high-speed elections Alpha (α) rays are a 2+ charged He nucleus

CONTINUED Rutherford’s gold foil experiment Atoms have a nucleus Atoms are made up mostly of space Protons exist in the nucleus with a + charge Electrons mass is 9.11 x kg, the charge is - NUCLEUS Protons mass is 1.67 x kg, the charge is + Neutrons mass is 1.66 x kg, there is no charge Called hadrons and are made up of quarks OUTER REGION Electrons - negative charge e - Called leptons Has an anti-particle called a positron.

CONTINUED AMU means x kg, so Atoms are small Diameters between 1 x m to 5 x m, Ǻ= 1 x m so it is 1 to 5 Ǻ Isotopes have the same number of protons but different number of

PERIODIC TABLE Chemical properties of elements depend upon their atomic number (Z), this can be seen in the periodic table The table is organized in the following way Period Horizontal rows Group Vertical columns Main group elements are columns 1, 2, Transitional elements are found in columns 3-12

SPECIAL NAMES Group 1 are called the ALKALI METALS Group 2 are called the ALKALINE EARTH METALS Group 17 are called the HALOGENS Group 18 are called the NOBLE GASES

MOLECULES No charge, usually they are made up of non-metals Group of two or more atoms held by strong forces called chemical bonds (covalent bonds) A structural formula shows the bonding pattern in the molecule

EXAMPLES IONS Metal atoms that become charged particles are called - cations (+) Nonmetal atoms that become charged particles are called - anions (-)

CONTINUED Number of protons remain unchanged in an ion compared to the atom Number of electrons increase if you are forming an anion Number of electrons decrease if you are forming a cation

IONIC COMPOUNDS Nature of ionic compounds They are made up of two oppositely charged ions - These compounds are held together by the charge attraction called an Ionic Bond Monoatomic ions Will have the same number of electrons as the neighboring noble gas (the one they are the closest to) ISOELECTRONIC SPECIES

IONS Some transition elements will form more than one ion Cu +, Cu 2+, Cr 3+, Cr 6+ Many compounds are ionic compounds NaCl, (NH 4 ) 2 SO 4, NaHCO 3 Polyatomic ions Contains more than one atom

NAMING MOLECULAR COMPOUNDS Molecules do not have charges so you must be told how many of each atom you have There will only be two elements in any of the molecular compounds given Always two nonmetals or semimetals

CONTINUED Use latin prefixes to tell how many atoms you have one – monotwo – di three – trifour – tetra five – pentasix – hexa seven – hepta eight – octa nine – nanaten – deca

BINARY MOLECULAR COMPOUNDS The first word gives the name of the element that appears first in the molecular formula. A Greek prefix is used to show the number of atoms A Greek prefix and the suffix -ide is added to the second name of the element in the molecular formula

ACIDS Molecular compounds which ionize in water to form hydrogen ions called Hydrohalic acid HX Polar molecule HCl + H 2 O --> H + (aq) + Cl - (aq) What would the aqueous solution of hydrogen bromide called Hydro-brom-ic Oxoacid contains oxygen and hydrogen Sulfuric acid H 2 SO 4, hydrogen removed from oxygen If the anion ends with –ate then acid is –ic if the anion ends with –ite then acid is -ous Chloric acid HClO 3 A hydrate is where water is contained in the formula