8 More practice: How many protons and electrons are in: a. radon b. magnesiumAn atom of an element contains 66 electrons. What element is it?An atom of an element contains 14 protons. What element is it?
9 Isotopes and Mass number Dalton was incorrect about atoms being indivisible and stating that all atoms of an element are identical. (#2 and #5)All atoms of a particular element have the same number of protons and electrons but the number of neutrons in the nucleus can differ.Isotopes – atoms with the same number of protons but different numbers of neutrons
10 Mass number = atomic # + # neutrons IsotopesAll Isotopes of a specific element have the same chemical behavior (determined by electrons)Isotopes are identified with a mass numberMass number = atomic # + # neutrons
12 Isotope notationIn nature most elements are found as a mixture of isotopesEx: copper – two types found naturally- 29 protons and 34 neutrons- 29 protons and 36 neutronsCu – 63; Copper – 63, 63Cu, 6329CuCu – 65; Copper – 65, 65Cu, 6529Cu
13 Mass of atomsAtoms are measured in amu (atomic mass units). (based on carbon -12)1 amu is almost equal to 1 proton or neutronAtomic mass – the weighted average mass of the isotopes of that element. Because isotopes have different masses, the weighted average mass is NOT a whole number.
14 For the following: Determine the number of protons, electrons, and neutrons. Name the isotope and give its symbol.ElementAtomic #Mass #Neon1022Calcium2046Oxygen817Iron2657Zinc3064Mercury80204
16 PracticeCalculate the atomic mass of unknown Element X. Identify the unknown element.IsotopeMass (amu)Percent Abundance6X6.0157.59%7X7.01692.41%
17 Boron has two naturally occurring isotopes: boron-10 (abundance =19 Boron has two naturally occurring isotopes: boron-10 (abundance =19.8%; mass = amu) and boron-11 (abundance = 80.2% and mass = amu) . Calculate the atomic mass of boron.