8More 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?
9Isotopes 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
10Mass 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
12Isotope 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
13Mass 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.
14For the following: Determine the number of protons, electrons, and neutrons. Name the isotope and give its symbol.ElementAtomic #Mass #Neon1022Calcium2046Oxygen817Iron2657Zinc3064Mercury80204
16PracticeCalculate the atomic mass of unknown Element X. Identify the unknown element.IsotopeMass (amu)Percent Abundance6X6.0157.59%7X7.01692.41%
17Boron 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.