1. Atomic Structure & Isotpes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

3. Structure of the Atom

5. nucleus nucleus – positive protons and neutral neutrons – 99.9% of the atom’s mass is here – up to 100,000 times smaller than the entire atom electrons are in space “around” the nucleus. negative electrons are in space “around” the nucleus.Nucleus Electron cloud Bill Nye atom size (start at 3:55)

6. sub-atomic particles Protons (p + ) Protons (p + ) – + electrical charge – same as atomic # on periodic table – 1.007 atomic mass units (amu) but we can round to 1 amu (mass = 1.672623 x 10 -24 g) Electrons (e - ) Electrons (e - ) – negative electrical charge – same as + protons in a neutral atom – 0.0005 amu but we can round to 0 Neutrons (n o ) Neutrons (n o ) – no electrical charge – mass = 1.009 amu but we can round to 1 amu

7. ParticleChargeMass (atomic mass units) Location Protonpositive + 1nucleus Neutronneutral Ø 1nucleus Electronnegative - 0.0006 or Ø orbit, level, cloud

9. Learning Check An atom has 14 protons and 20 neutrons. A.Its atomic number is 1) 142) 163) 34 B. Its mass number is 1) 142) 163) 34 C. The element is 1) Si2) Ca3) Se D. The number of electrons is 1) 142) 63) 20

10. Even smaller particles quarks – make protons & neutrons – 6 types He

11. Isotopes same element but differ in their number of neutrons the mass number on periodic table is the WEIGHTED AVERAGE MASS of all the isotopes of that element – this is based on an isotope’s natural abundance the percentage of each isotope of an element that occurs in nature

15. 2.3

18. Chemical symbols for isotopes two different ways to write isotopes – example sodium sodium- 23 – only shows total mass (23) of the sodium isotope 23 Na – shows the total mass (23) and the atomic # (11) of the sodium isotope 11 X Mass Number Atomic Number Element Symbol

19. Isotopes? Which of the following represent isotopes of the same element? Which element? 234 X 234 X 235 X 238 X 92 93 9292

20. How many protons, neutrons, and electrons are in-- C 14 6 How many protons, neutrons, and electrons are in-- C 11 6 6 protons, 8 (14 - 6) neutrons, 6 electrons 6 protons, 5 (11 - 6) neutrons, 6 electrons Do You Understand Isotopes?

21. H 1 1 H 2 1 H 3 1 U 235 92 U 238 92