1. Structure of the Atom – Atomic Facts Ch 03 notes

2. Structure of the atom The atom has TWO main parts: 1.Nucleus 2.Electron Cloud Atoms are electrically neutral A.Overall charge of an atom is ZERO B.electrons = protons

3. The Nucleus Central portion of atom Make up most of the mass of the atom Contains two subatomic particles protons – positive charge(+) makes the atom unique 1.67266 x 10 -27 kg neutrons –neutral, no charge(0) this number can change—still have same element “isotope” 1.67495 x 10 -27 kg

4. Electron Cloud surrounds the nucleus electrons –negative mass of the electron is = 9.11 x 10 -31 kg Sub-atomic particle involved in bonding

5. Atomic Facts atomic number the number of PROTONS in the nucleus Average atomic mass the average mass of an atom of this element, expressed in atomic mass units. o Because atoms are so small we use an atomic mass unit(u) = to find the mass of one atom  1 amu = 1.66 X 10 -24 g 6 12.0107 C Carbon

6. Isotopes Atoms of the same element with a different number of neutrons. http://education-portal.com/academy/lesson/isotopes-and- calculation-of-a-weighted-average.htmlhttp://education-portal.com/academy/lesson/isotopes-and- calculation-of-a-weighted-average.html Average atomic mass is a weighted average of these isotopes Isotopes have a different mass number but identical atomic number The MOST COMMON isotope is represented on the PTE!!! https://www.youtube.com/watch?v=pV822HfqT44

7. Writing Isotopes Bromine-79 Bromine-81 http://www.webelements.com/isotopes.html More EX: Oxygen, Boron,

8. Atomic Facts o Mass number – number of protons + neutrons in the nucleus---whole number o IF NOT GIVEN: Round avg. atomic mass to nearest whole number. Mass number – atomic number = neutrons The number of protons = the number of electrons– atoms are electrically neutral 8 15.999 O Oxygen Oxygen-16

9. Cl 35.453 17 Chlorine Isotopes of Chlorine: Chlorine-35 and Clorine-37 Isotopes of Bromine: Bromine-79 and Bromine-81 http://education-portal.com/academy/lesson/isotopes-and-calculation-of-a-weighted- average.html 35 79.904 Br Bromine https://www.youtube.com/watch?v=pV822HfqT44

10. Calculating Average Atomic Mass What you need: Percent (%) abundance of each isotope in decimal form Mass( in amu’s) of each isotope of the element How to calculate the weighted average by: 1.(mass isotope 1) (percent abundance in decimal form)= 2.(mass isotope 2) ( percent abundance in decimal form)= 3.(mass isotope 3) ( percent abundance in decimal form)= ADD ALL TOGETHER!!!

11. Calculate the Average Atomic Mass Mass of Isotope Abundance 24.0 amu 78.70% 25.0 amu 10.13% 26.0 amu 11.17% Calculate the average atomic mass. What element is this?

12. Calculate the Average Atomic Mass A certain element is a soft, silvery-white metal that has two common isotopes, the first isotope has a mass of 85.0 amu’s the second isotope has a mass of 87.0 amu’s. If the abundance the first isotope is 72.2% and the abundance of the second isotope is 27.8%, what is the average atomic mass of this element? What is the element?

13. Atomic Facts Chemical symbols – the abbreviated way to write the name of an element –a capital letter –cap letter AND lower case letter. –Others come from their Latin name ( Argentum Ag : silver) Co vs. CO Metal that forms bright blue solid compounds. Poisonous gas