Transcript Mass number
Isowhat? Man, you trippin’ nephew. Isotopes If you change the It will affect the… And the result number of… will be a… Protons Electrons Neutrons If you change the It will affect the… And the result number of… will be a… Protons Identity of the atom Completely different atom Mass Isotope Electrons Neutrons What Are Isotopes? • They are atoms of the same element that have different numbers of neutrons. It’s just a change in the neutrizzle fo shizzle!!! An Example • Hydrogen has 3 isotopes – There are 3 different “versions” of a hydrogen atom 1. 1 proton and 0 neutrons (mass number = 1) 2. 1 proton and 1 neutron (mass number = 2) 3. 1 proton and 2 neutrons (mass number = 3) Note how the number of protons never change!!! Example: Magnesium • Has 3 isotopes # protons # neutrons Mass (amu’s) % abundance Isotope 1 12 12 24 79% Isotope 2 12 13 25 10% Isotope 3 12 14 26 11% % abundance?????? • Every isotope is found in nature in a fixed percentage. • In other words, 79% of the magnesium atoms in any “scoop” of magnesium found anywhere in the universe will be magnesium atoms with 12 neutrons, 10% of the atoms in the scoop will have 13 neutrons, and 11% will have 14 neutrons. – These percentages are different for each element…you just have to look them up to find out what they are. The Vocabulary Section Terms associated with isotopes A Few Important Terms Ya Gotta Know • Atomic number = the number of protons – It’s the same as the element’s position on the periodic table – For example, carbon is the 6th element on the table, so its atomic number is 6 which means it has 6 protons (and 6 electrons if it’s a neutral atom) A Few Important Terms You Gotta Know • Atomic mass = the “weighted” average mass of all the different isotopes of an atom – This is the “weird” number on the periodic table that usually has a bunch of places past the decimal point A Few Important Terms You Gotta Know • Mass number = # of protons + # of neutrons – This one kind of makes sense because remember we said the electrons essentially don’t have any mass – This HAS to be a whole number!!!!! – It has to be, because you can’t have part of a proton or neutron – Mass number is NOT given on the periodic table O.K. nephew…try these examples, then we can chill ‘till the next episode… Let’s Practice Those Terms… 1. What is the mass number of a carbon atom that has 6 neutrons? 7 neutrons? 2. How many neutrons does a nitrogen atom have if its mass number is 14? 3. How many neutrons does a chlorine atom have if its mass number is 37? 4. What is the atomic number of neon? Answers 1. 2. 3. 4. 12 and 13 7 19 10 A ZX Notation for Isotopes A shorthand way to write isotopes A Short Way to Write Isotopes A Z X “X” will be the symbol of the element Problem #1 1. Write az X notation for an isotope that has 17 protons and 18 neutrons. Problem #2 • Write azX notation for an isotope that has 19 protons and 21 neutrons. Different Forms of • 35 Cl 17 AX Z is the same as 35Cl17 • Might also see “Cl-35” or “chlorine-35”