Chemical Structure: A review

1. Chemical Structure: A review • All matter is made of elements combined in some way, all elements are made of atoms. • Matter can exist in three states of increasing atomic/molecular kinetic energy-solid(slowest), liquid, gas(fastest). • Atoms are composed of protons, neutrons, and electrons • me=9.109 x 10-31kg • mn=1.675 x 10-27kg • Neutrons and protons differ slightly in mass, where the mass of a proton is 1.675 x 10-27kg • Protons and neutrons are over 1800x the size of electrons 1 proton=1amu=1neutron

2. Atomic Structure The protons and neutrons are contained in the nucleus, and the electrons circulate the nucleus in the “electron cloud” that is composed of different energy levels

3. Brief Atomic History Democritius (400BC) thought matter made of “atomos” Dalton (very early 1800s)) atoms made of little balls “cue ball theory” Thomson (late 1800s) discovered electrons “plum pudding model” using cathode ray tube Rutherford (early 1900s) gold foil experiment proved existence of positive nucleus Chadwick (1932) discovered neutrons Both Chadwick and Rutherford used the experiments in radiation of Marie Curie (late 1800s early 1900s) to support and inspire their experiments

4. Forces that Rule • Four forces rule everything in the universe • Gravitational: an effect objects have on space time around them • Electrostatic: attraction between unlike charges, repulsion between like charges • Weak Nuclear Force: causes some nuclei to decay (radioactive decay) • Strong Nuclear Force: holds nucleus of atom together created by a balance of protons and neutrons

5. Nuclear Chemistry deals in the strong and weak nuclear forces • Gravity effects all • Traditional chemistry concentrates on electrostatics. • The movement of electrons is what causes ALL chemical reactions • Elements/compounds react in order to create a more stable electronic structure (spontaneously) • In order to create a less stable structure, energy must be put into the system ex heat, light, or a catalyst

6. Basic Laws to Follow • Law of Conservation of Mass:mass(matter) cannot be created or destroyed, it can only change form • Law of Definite Proportion: a given compound always contains exactly the same proportion of elements by mass • H20 is water, dihydrogen oxide, and nothing else • H2O2 is hydrogen peroxide and nothing else • Each compound has its own set of chemical and physical characteristics • Both of these laws first publish by Dalton

7. Basic Laws Cont • Law of Multiple Proportions: when two elements form a series of compounds, the ratios of the masses of the second element that combine with one gram of the first element can always be reduced to small whole numbers • Look at three different compounds containing nitrogen and oxygen. They were compared by seeing what masses of nitrogen would combine with 1g of oxygen

8. Mass of nitrogen that combines with 1g of oxygen **********Just because its mathematically possible doesn’t mean its stable in nature!

9. Basics of Chemical Reactions • Electrons of an atom circulate the nucleus in shells, or levels of the electron cloud • The innermost shell is K, the outermost(so far) is Q • Within those shells, electrons circulate in orbital sub-shells s,p,d, or f • s subshells have 2 electrons, p subshells have 6, d subshells have 10, and f subshells have 14 electrons • Atoms strive to have a filled outermost shell to achieve maximum stability

10. Isotopes • Chemical properties are identical since electron and proton number is the same between isotopes of the same element • Only NEUTRON number changes • Isotopes have many uses such as in nuclear medicine

11. Mass Spectroscopy • Separates sample into its components by weight

12. How to Read a Mass Spec • Look at atomic mass of carbon…how many isotopes do you expect? • Since atomic mass is very close to exactly 12, implies very few other isotopes

13. Chlorine Write the two isotopes shown for chlorine, which is the most common isotope?

14. What about water? Looking at atomic masses on Periodic table for Oxygen, where do you think the different isotopes occur, Hydrogen or Oxygen?

15. Valance electrons govern chemical reactions How are the electrons organized????? How does this determine reactivity? • For non-transition metals, elements strive to achieve the Octet rule • This means they will gain, lose, or share electrons in order to fill the s and p subshells of a given shell (K,L,M…..) • Do this as easily as possible, look at potassium……what is its valance electron status?

16. The Shape of the Periodic Table is to show the elements that have outermost subshells of a certain level

17. Valance electron is the one in the outermost shellSince it is much easier to give up that one electron to go back to a filled 3s and 3p level (octet rule filled) than gain 7 electrons, Potassium will readily react with anything, like water, that it can give up its one electron to.

18. The names of the electron shells come from a fellow named Charles G. Barkla, a spectroscopist who studied the X-rays that are emitted by atoms when they are hit with high energy electrons. He noticed that atoms appeared to emit two types of X-rays. The two types of X-rays differed in energy and Barkla originally called the higher energy X-ray type A and the lower energy X-ray type B. He later renamed these two types K and L since he realized that the highest energy X-rays produced in his experiments might not be the highest energy X-ray possible. He wanted to make certain that there was room to add more discoveries without ending up with an alphabetical list of X-rays whose energies were mixed up.As it turns out, the K type X-ray is the highest energy X-ray an atom can emit. It is produced when an electron in the innermost shell is knocked free and then recaptured. This innermost shell is now called the K-shell, after the label used for the X-ray. Barkla won the 1917 Nobel Prize for Physics for this work.

19. Electrons fill in order of lowest energy subshells first, follow the pattern of the period table

20. Hund’s Rule • Hund's rule: every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied, and all electrons in singly occupied orbitals have the same spin s orbitals have one subshell, p have three, d have 5, f have 7…just remember electrons like to go in pairs!

21. Pauli exclusion principle: Electrons in each subshell must have opposite spins • http://commonsensequantum.blogspot.com/2010/10/explaining-electron-spin-and-pauli.html

22. Schrodinger’s CatParticle Duality Goes with Heisenberg, you can never know exactly where an electron is and its path at the same time “Uncertainty Principle”