Presentation on theme: " Atomic Number- the number of protons in the nucleus of an atom of that element Ex: Hydrogen atoms have only one proton in the nucleus, so the atomic."— Presentation transcript:
Atomic Number- the number of protons in the nucleus of an atom of that element Ex: Hydrogen atoms have only one proton in the nucleus, so the atomic number is 1. Atoms are neutral, so the # of protons =# of electrons.
Total number of protons and neutrons in an atom. Mass = # protons + # neutrons The # of neutrons in an atom is the difference between mass # and atomic #. # Neutrons = Mass # - Atomic #
Atoms that have the same # of protons, but different # of neutrons. If they have more/less neutrons, then the mass number will be different! Have same number of protons and electrons. Only difference is # of neutrons!
A way to measure the mass of an atom, using a standard (carbon-12). Carbon-12 has 6 protons and 6 neutrons. It’s mass is set at 12 amu. So the mass of a single proton or neutron is about 1 amu. Atomic Mass- weighted average mass of the atoms in a naturally occurring sample of the element.
1. Change abundance percents into decimals. 2. Multiply the mass of each isotope by its natural abundance. (expressed as decimal) 3. Add the products.
Element X has two natural isotopes. The isotope with a mass of 10.012 amu has a relative abundance of 19.91%. The isotope with a mass of 11.009 amu has a relative abundance of 80.09%. Calculate the atomic mass and identify this element.
The element copper has naturally occurring isotopes with mass numbers of 63 and 65. The relative abundance and atomic masses are 69.2% for mass = 62.93 amu, and 30.8% for mass = 64.93 amu. Calculate the average atomic mass of copper.
Calculate the atomic mass of bromine. The two isotopes of bromine have atomic masses and relative abundance of 78.92 amu (50.69%) and 80.92 amu (49.31%).