ATOMICSTRUCTURE Semester Chemistry Unit 2 KNOCKHARDY PUBLISHING

LecturePLUS Timberlake2 Atomic Theory Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements Two or more different atoms bond in simple ratios to form compounds

THE STRUCTURE OF ATOMS Atoms are the smallest particles of an element that have the properties of that element. They consist of a number of fundamental particles, the most important are... Location Relative charge Relative mass (amu) PROTONNucleus+11 NEUTRONNucleus01 ELECTRONElectron shells1/1837

MASS NUMBER AND ATOMIC NUMBER Atomic Number (Z)Number of protons in the nucleus of an atom Mass Number (A) Sum of the protons and neutrons in the nucleus Ions: Atom or electron that has lost or gained electrons.

MASS NUMBER AND ATOMIC NUMBER Atomic Number (Z)Number of protons in the nucleus of an atom Mass Number (A) Sum of the protons and neutrons in the nucleus Na Mass Number (A) PROTONS + NEUTRONS Atomic Number (Z) PROTONS

MASS NUMBER AND ATOMIC NUMBER Atomic Number (Z)Number of protons in the nucleus of an atom Mass Number (A) Sum of the protons and neutrons in the nucleus Na Mass Number (A) PROTONS + NEUTRONS Atomic Number (Z) PROTONS THESE ALWAYS GO TOGETHER – ANYTHING WITH 11 PROTONS MUST BE SODIUM

MASS NUMBER AND ATOMIC NUMBER Atomic Number (Z)Number of protons in the nucleus of an atom Mass Number (A) Sum of the protons and neutrons in the nucleus Na Mass Number (A) PROTONS + NEUTRONS Atomic Number (Z) PROTONS

MASS NUMBER AND ATOMIC NUMBER Atomic Number (Z)Number of protons in the nucleus of an atom Mass Number (A) Sum of the protons and neutrons in the nucleus Na Mass Number (A) PROTONS + NEUTRONS Atomic Number (Z) PROTONS THERE WILL BE 12 NEUTRONS IN THE NUCLEUS 23 – 11 = 12

MASS NUMBER AND ATOMIC NUMBER Atomic Number (Z)Number of protons in the nucleus of an atom Mass Number (A) Sum of the protons and neutrons in the nucleus Na Mass Number (A) PROTONS + NEUTRONS Atomic Number (Z) PROTONS

MASS NUMBER AND ATOMIC NUMBER ProtonsNeutronsElectronsCharge Atomic Number Mass Number Symbol A B20040 C+1123 D660 E F613 G H 27 Al 3+

MASS NUMBER AND ATOMIC NUMBER ProtonsNeutronsElectronsCharge Atomic Number Mass Number Symbol A K B Ca C Na + D C E U F C G S 2- H Al 3+

RELATIVE MASSES Relative Atomic Mass (A r ) The mass of an atom relative to the 12 C isotope having a value of A r =average mass per atom of an element x 12 mass of one atom of carbon-12 Relative Isotopic Mass Similar, but uses the mass of an isotope 238 U Relative Molecular Mass (M r ) Similar, but uses the mass of a moleculeCO 2, N 2 Relative Formula Mass Used for any formula of a species or ionNaC l, OH¯

LecturePLUS Timberlake14 Atomic Mass Atomic mass is the weighted average mass of all the atomic masses of the isotopes of that atom.

LecturePLUS Timberlake15 Example of an Average Atomic Mass Cl-35 is about 75.5 % and Cl-37 about 24.5% of natural chlorine. 35 x 75.5 = x 24.5 =

ISOTOPES DefinitionAtoms with… the same atomic number but different mass number or the same number of protons but different numbers of neutrons. PropertiesChemical properties of isotopes are identical Physical properties (such as density) can differ

LecturePLUS Timberlake17 Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl17 chlorine - 35 chlorine - 37

LecturePLUS Timberlake18 Learning Check Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12 C 13 C 14 C #p _______ _______ _______ #n _______ _______ _______ #e _______ _______ _______

LecturePLUS Timberlake19 Solution 12 C 13 C 14 C #p #n #e 6 6 6

ISOTOPES DefinitionAtoms with… the same atomic number but different mass number or the same number of protons but different numbers of neutrons. PropertiesChemical properties of isotopes are identical Physical properties (such as density) can differ TheoryAtoms of the same element can have different masses due to the variation in the number of neutrons in the nucleus. The atomic mass was a consequence of the abundance of each type of isotope. ProtonsNeutrons 1 H H H 1 12 ISOTOPES OF HYDROGEN

ISOTOPES - CALCULATIONS There are two common isotopes of chlorine. Calculate the average relative atomic mass of chlorine atoms ProtonsNeutrons% 35 Cl Cl

ISOTOPES - CALCULATIONS There are two common isotopes of chlorine. Calculate the average relative atomic mass of chlorine atoms Method 1 Three out of every four atoms will be chlorine-35 Average = = ProtonsNeutrons% 35 Cl Cl

ISOTOPES - CALCULATIONS There are two common isotopes of chlorine. Calculate the average relative atomic mass of chlorine atoms Method 1 Three out of every four atoms will be chlorine-35 Average = = Method 2 Out of every 100 atoms 75 are 35 Cl and 25 are 37 Cl Average = (75 x 35) + (25 x 37) = ProtonsNeutrons% 35 Cl Cl