Download presentation
Presentation is loading. Please wait.
Published byHeaven Hatchett Modified over 10 years ago
1
How Atoms Differ October 2, 2014
2
Reading an Element A – Atomic Number: the number of protons in an atom (this identifies the element) B – Average Atomic Mass C – Chemical Symbol D – Chemical Name
3
Atomic Number - Z All atoms are neutral, the charges of the protons and electrons must cancel each other out Atomic Number = number of protons = number of electrons Fill in the table below. Element Atomic Number ProtonsElectrons Pb82 8 30
4
Isotopes Isotopes are atoms with the same number of protons but different number of neutrons. The atomic number stays the same Mass will change, since neutrons have a relative mass of 1
5
Isotope Notation Mass Number – the sum of the atomic number(or number of protons) and neutrons in the nucleus These are both saying that the element is carbon, it has a mass number of 14, atomic number of 6 So 6 protons, 6 electrons, and 8 neutrons Carbon -14
6
Fill in the table below ElementMass #Atomic # Protons & Electrons Neutrons Isotope Symbol Neon2210 Calcium4620 Oxygen178 Iron5726 Zinc6430 Mercury20480
7
Atomic Mass An Elements mass is made up of protons (1 amu) and neutrons (1 amu) However an elements mass is usually never a whole number. Atomic Mass of an element is the weighted average mass of the isotopes of that element
8
Calculating Atomic Mass Chlorine – 35 has a mass of 34.969 amu, a percent abundance of 75.78% Chlorine – 37 has a mass of 36.966 amu, a percent abundance of 24.22% Calculate the mass contribution of each isotope Chlorine – 35: (34.969 amu x 75.78%) = 26.500 amu Chlorine – 37: (36.966 amu x 24.22%) = 8.9532 amu Now add the isotopes mass contribution together to get your weighted average atomic mass (26.500 amu + 8.9532 amu) = 35.453 amu The weighted average atomic mass should be the same or very close to what is on the periodic table.
9
Isotope Practice Boron has two naturally occurring isotopes: boron – 10 (abundance = 19.8%, mass = 10.013 amu) and boron – 11 (abundance = 80.2%, mass = 11.009 amu). Calculate the mass of boron. Identify the unknown element X, based on the information given in the table. Nitrogen has two naturally occurring isotopes, N -14 and N- 15. Its atomic mass is 14.007 amu. Which isotope is more abundant? Explain. IsotopeMass (amu)Percent Abundance X – 66.0157.59% X - 77.01692.41%
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.