Matter & Energy

1. Matter & Energy Foundations of the Natural World

2. Matter • If it exists, it’s matter • You, a rock, oxygen… • has mass; takes up space (volume) • Fundamental unit: the atom • Atoms vary by # of protons • each a different element • Organized into the periodic table • Can be changed, yet is always conserved

3. Energy • Makes things happen • Do work • Reorganize matter • Comes in different forms • in the chemical bonds of the food we eat • radiant energy from the sun • Can be changed, yet is always conserved

4. Mass is energy? • In the early 20th century, scientists hypothesized that mass and energy are linked. • Albert Einstein provided the mathematical evidence with his famous equation, E = mc2 • "E" ="energy," • "m" denotes "mass" • "c" is the speed of light

6. New Boys Atomic structure Pro’s Elected ones the ‘hood WKRP atomic structure.webloc

7. Atomic structure neutron atomic nucleus Proton: + charge Electron: - charge

8. Sub-atomic structure Some sub-atomic particles have sub-particles themselves! Up quark charge +2/3 Down quark charge -1/3 Do the math! p = 2 ups, 1 down n = 1 up, 2 down e- ? Its a fundamental particle

9. Unstable nuclei Potential problem in nucleus : like charges (++) repel Neutrons break up charge; if they can’t, particles are ejected • changes the number of protons • changes the element • a radioactive atom (more in C/D IS year)

10. Electrons orbit the nucleus Orbit model vs Orbital model • Negative electrons orbit the positive nucleus The first - nearest the nucleus - can hold up to 2 e- The others hold 8e- or more , but are ‘full’ once they have 8

11. Element info element atomic number = protons infer electrons If p <> e, then an ion symbol atomic mass = nuclear mass # protons + neutrons why .003? Isotopes!

12. Isotopes vary in # of neutrons Isotopes of H 1 a.m.u.* 2 a.m.u. 3 a.m.u. *a.m.u. = 1 atomic mass unit number of nuclear particles = mass number

13. Electron dot model* – shows valence e- The number of e- in the outermost orbitDetermines if the atom will form bonds 12 e- 2•18•2 valence e- 10 e- 2•8•8 valence e- 6 e- 2•8•4 valence e- *aka Lewis dot

14. Oxidation Number determinedby valence e- Determines which atoms are likely to bond with which other atoms is the outer orbit more empty, or more full? 2 valence e- • donates 2 • +2 oxidation # 6 valence e • accepts 2 • -2 oxidation # It’s a match!

15. Periodic patterns Groups - Same valence/oxidation # Periods - Same # shells/orbits No stable isotopes synthetic the element song

16. Periodic patterns Periods - Same # shells/orbits No stable isotopes synthetic the element song

17. 11 p+ 17 p+ 11 e- 17 e- Ionic bonds Valence stability achieved by moving an electron to another atom Creates charge imbalance Atoms become ions Positive & negative ions attracted to one another Oppositely charged ions form an ionic bond - + 11p+ 17P+ 10 e- 18 e-

18. Another view Oxidation: +1 -1 p+ to e- ratio: 11:10 17:18

19. Covalent bonds Atoms have an equal attraction to the electrons Share electrons Electrons orbit both atoms equally

20. Polar covalent bonds + Electrons more attracted to one atom type – reflects electronegativity Share e- unequally - + Result? Regions of molecule are weakly positive and negative

21. Ionic Bonds metal with non- metal very different valences electrons donated/accepted ex: NaCl 1 7 Na Cl go either way

22. Covalent Bonds Non-metal with non-metal similar valences electrons shared ex: CO2 4 6 C O go either way