2 State StandardsCLE – Describe the structure and arrangement of atomic particles
3 What is an Atom?The three main components of an atom are distinquished by mass, charge, and locationThe chemistry of each element depends directly on these three componentsNucleus:Protons ( positively charged )Neutrons ( neutral – NO CHARGE )Electrons ( negatively charged )
4 Electric Forces in Atoms Protons and electrons attract each otherElectric force holds components together; the same forces hold solids and liquids togetherLiquid water is held together by electric forces
5 Atomic Components Protons ( +1 charge / 1.67 x 10-27 kg ) Neutrons ( 0 charge / 1.67 x kg )Electrons ( -1 charge / 9.11 x kg )All ( most ) elements contain all threeAtoms of the same element contain the same number of protons, but neutrons may varyEach element has a unique number of protons
6 Distinguishing Elements and Atoms Atomic number – number of protons in an atomMass number – number of protons & neutronsIsotopes – exist for an element if different atoms ( with the same atomic number ) have varying numbers of protons ( different mass numbers )
7 Hydrogen & HeliumHydrogen ( H ) contains 1 electron, 1 proton, and 0 neutrons [ Protium isotope ]Helium ( He ) contains 2 electrons, 2 protons, and 2 neutronsWhat is atomic number, mass number of H, He?
8 Isotopes of Hydrogen Protium – Most common form on Earth and Sun 1 electron, 1 proton, 0 neutronsDeuterium – small fraction of hydrogen; 1 out of every 6,000 hydrogen atoms in Earth’s crust1 electron, 1 proton, 1 neutronTrillium – very unstable and so very rare1 electron, 1 proton, 2 neutrons
9 Isotopes of ChlorineThe common form of chlorine ( Cl ) has 17 protons, 17 electrons, and 18 neutronsAnother form has 20 neutronsNeutrons can be calculated by using theseHow do we know which form is most common?
10 Atomic Mass Units Used to express the mass of such tiny particles Unified Atomic Mass Unit is 1/12 the mass of a Carbon-12Carbon-12 isotope has a fairly even mass number6 protons and 6 neutronsRemember electrons contribute little mass to atomEach proton/neutron has mass of 1.0 uUnits given as a u
11 Atomic Mass UnitsThe value of AVERAGE ATOMIC MASS found in the periodic table tells us which isotope of any element is most common ( HYDROGEN )weighted average so most common form counts mostZinc with average atomic mass 65.4 u65 ( closest mass # ) – 30 ( atomic # ) = 35 neutronsMost common Zn isotope has 35 neutronsCl has average of u , with 35 mass numberMost common Cl form contains 18 neutrons
12 The MoleIn order to count large numbers of small particles, a COUNTING UNIT was devised – THE MOLE ( mol )Examples ( Avogadro’s number ):1 mol = 602,213,670,000,000,000,000,000 particlesEquals x 1023 when put into scientific notation1 mol of marbles = x 1023 marbles1 mol of atoms = x 1023 atoms ( any atom )1 mol of He atoms = x 1023 He atoms
13 The Mole How many stars in the universe? 2003, roughly 7 x 1022 stars counted ( within rangeValue could increase in future6.022 x 1023 popcorn kernels would cover the USA in a pile 500 km ( or 310 mi ) tall!!Avogadro’s number is used only for small particles
14 Relating Moles and Grams Mass of 1 mol random atoms difficult to findEach element has a unique MOLAR MASSThe mass of 1 mol of this type of atom ( element )Usually accounts for several isotopesMass of 1 mol of the same atom easy to findFor Carbon-12, molar mass is gMolar mass ( in g ) equals average atomic mass ( in u )Carbon-12 has u as well as g/molFigure 7 in text
15 Relating Moles and Grams Mass of 1 mol Carbon-12 atoms is gUSE PERIODIC TABLE24 g Carbon-12 = 2 mol Carbon-123 mol Carbon-12 = 36 g Carbon-12
16 Molar Mass of Compounds, Molecules As elements ( atoms with same atomic number ) have a MOLAR MASS, so do coumpoundsH2O : 2 Hydrogen with 1.00 g/mol & 1 Oxygen with 16 g/molGives ( ) g/mol = 18 g/molCO2 : 1 Carbon with g/mol & 2 Oxygens with 16 g/molGives ( ) g/mol = 44 g/molO2 : 2 Oxygen atoms at 16 g eachGives: 32 g/mol for O2 moleculesHO