1. I. Subatomic Particles (p.113 - 114)

2. ParticleSymbolLocationChargeRelative Mass (amu) Actual Mass (g) electron proton neutron e-e- p+p+ n0n0 Electron cloud nucleus – + 0 1/1840 1 1 9.11 x 10 -28 1.67 x 10 -24 approx 0

3.  Elements are listed by their chemical symbols  Symbols are usually either one capital letter like C for Carbon, or one capital and one lowercase letter like Ne for Neon

4.  The periodic table gives much information we need to learn more about the atom of each element

5.  Atomic number = # of protons in an atom  Whole number shown on periodic table  Periodic table is arranged by atomic number

6.  The average atomic mass is the number at the bottom of this square  Found by averaging the natural abundances of its isotopes  Weighted average

7. Atomic Number Symbol Element Name Atomic Mass

8. Protons Electrons ProtonsNeutrons # n 0 = Atomic mass – Atomic number

9. Most of the atom’s mass. NUCLEUS ELECTRONS PROTONS NEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE ATOM QUARKS #n 0 = Atomic mass - Atomic # equal in a neutral atom Atomic Number equals the # of...

10.  Quarks ◦ component of protons & neutrons ◦ 6 types  3 quarks = 1 proton or 1 neutron He

11. II. How Atoms Differ (p. 114 - 121)  Mass Number  Isotopes  Relative Atomic Mass  Average Atomic Mass

12.  mass # = protons + neutrons always a whole number NOT on the Periodic Table! © Addison-Wesley Publishing Company, Inc.

13.  Atoms of the same element with different numbers of neutrons Mass # Atomic # Isotope notation: Isotope name: carbon-12 Element name Mass #

14. © Addison-Wesley Publishing Company, Inc.

15.  Chlorine-37 ◦ atomic #: ◦ mass #: ◦ # of protons: ◦ # of electrons: ◦ # of neutrons: 17 37 17 20 Isotope notation:

16.  Most elements are found as mixtures of isotopes  Relative abundance of each isotope is the same in each source

17.  12 C atom = 1.992 × 10 -23 g 1 p= 1.007276 amu 1 n = 1.008665 amu 1 e - = 0.0005486 amu © Addison-Wesley Publishing Company, Inc. atomic mass unit (amu) 1 amu= 1 / 12 the mass of a 12 C atom

18.  weighted average of all isotopes  on the Periodic Table  round to 2 decimal places Avg. Atomic Mass

19. Avg. Atomic Mass  EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% 16 O, 0.04% 17 O, and 0.20% 18 O. 16.00 amu

20. Avg. Atomic Mass  EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37. 35.40 amu