1. Unit 2 – Lecture 3

2. Atoms smallest particle of an element that retains its chemical properties composed of subatomic particles protons (p + ), neutrons (n 0 ), & electrons (e - ) “sub-” = below, less than

3. Subatomic Particles Types of Subatomic Particles [p + ] – positively charged subatomic particle found in the nucleus of an atom relative mass = 1 amu [atomic mass unit] [n 0 ] – non-charged subatomic particle [neutral] found in the nucleus of an atom relative mass = slightly larger than 1 amu new theories: [p + ] + [e - ] = [n 0 ] ?

4. Subatomic Particles – cont’d [e - ] – negatively charged subatomic particle found outside of the nucleus in energy levels [aka e - clouds, e - shells, etc] no relative mass [actual mass is 1/1936 th of 1 amu…] Quarks? theoretically = smaller particles that make up (p + ), (n 0 ), & (e - ) have their own branch of “theoretical physics”

5. Discuss Which subatomic particle is neutral? Which describes a single particle of an element? Which subatomic particle is negative? Which subatomic particle may or may not exist? Which is a single particle of a compound? Which subatomic particle is positive?

6. Elements Elements are made of atoms. atomic number – number of e - or p + chemical symbol – name of element atomic mass – number of “nucleons” nucleon = particle in the nucleus ie, the mass of p + plus mass of n 0

7. Elements – cont’d Elements are found on the periodic table in their natural, neutral state meaning, they’re neutral = same # of p + & e -

8. Discuss - Oxygen atomic mass? number of protons? atomic number? number of electrons? chemical symbol? number of neutrons?

9. More Practice An atom with 4 protons and 6 neutrons would: have a mass of…? have an atomic number of…? have … electrons typically? be which element?

10. Writing Elements - Silver Write: Chemical Symbol Mass Number at the upper-left of the symbol Atomic Number at the lower-left of the symbol Charge [if applicable] at the upper-right hand corner NOT ALL OF THESE ARE NECESSARY Ag 108 47 +4

11. Counting Particles p + s = Atomic Number [17] n 0 s = Atomic Mass – Atomic Number [35-17 = 18] e - s = p + s [17] Cl 35 17

12. Counting Particles – cont’d if e - s differ called ion charge is different more e - s [than normal] = more negative charge less e - s [than normal] = more positive charge

13. Counting Particles – cont’d if n 0 s differ called isotope “iso-” = equal/same same chem & phys properties atomic mass on periodic table is average of isotopes if p + s differ is a different element

14. Isotopes – Examples

15. Different Atoms, Same Element Allotrope – different natural/physical forms of an element “allo-” = other/different Ex. for Carbon: Graphite, Diamond, Buckminsterfullerenes [buckyballs]… Ex. for Oxygen: [O 2 ], Ozone [O 3 ]

16. Allotropes of Carbon a.diamond b.graphite c.lonsdaleite d.buckyballs [C60 – buckminsterfullerene] e.C540 f.C70 g.“amorphous” carbon [not truly amorphous] h.single-walled carbon nanotube / buckytube

17. Allotropes of Oxygen

18. Electron-Dot Models p + s & n 0 s exist in the nucleus e - s exist in electron/energy shells around the nucleus “octet rule” - atoms will gain, lose, or share e - s to become chemically stable [8 e - s in valence shell] valence shell = outer-most shell e - s in valence shell = valence e - s

19. Electron-Dot Models Draw Nucleus Protons Neutrons

20. Electron-Dot Models – cont’d Draw Electrons Electron Levels *2* up to 8…

21. Discuss Atoms are the smallest particle of elements, compounds, homogeneous mixtures, heterogeneous mixtures Which subatomic particle has a neutral charge? protons, neutrons, electrons, quarks What is the dense center of an atom called? protium, nucleus, neutron core, core

22. Discuss Which property discerns atoms from one another? atomic mass, mass number, atomic number, none of the above Atomic Number is based on which property of atoms? # of protons, # of electrons, # of neutrons, total # of particles

23. Discuss The total number of nucleons is atomic mass, atomic number, nucleon count, state of matter Atoms of an element with different number of neutrons are allotropes, isotopes, megatopes, gigatropes Which subatomic particles are not included in calculating Atomic Mass? protons, neutrons, electrons, nucleons

24. Discuss How many neutrons are in Oxygen-16, which has an atomic number of 8? [# denotes mass] 4, 6, 8, 10, 12, 14, 16 How many neutrons are in Oxygen-18, which has an atomic number of 8? 4, 6, 8, 10, 12, 14, 16 Which subatomic particle has a positive charge? Protons, Neutrons, Electrons, Quarks How many e - s fit in an atom’s first electron level?

25. Homework Complete - page 13 - # of Atoms in a Formula w/s DO NOT COMPLETE GRAM FORMULA MASS w/s IN THE MIDDLE OF PAGE 13. - BOTTOM of pg 13-top of 14 Parts of An Atom [CHART]