Basics of Chemistry: Elements, Atoms, and Bonds

1. Introduction to Chemistry

2. Objectives… • Define chemical element, atom, ion, molecule and compound • Explain how chemical bonds form • Describe what happens in a chemical reaction and explain why it is important to the human body

3. Chemical Element • Substances that cannot be broken down by normal chemical means • ~112 known chemical elements • Each is designated by a chemical symbol

4. 26 elements are found in the human body • 96% of the body’s mass is made from Carbon, Hydrogen, Oxygen and Nitrogen • 3.8% is from Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium and iorn

5. Trace Elements • The remaining 0.2% of the body’s mass is made of these 14 elements: • Al, B, Cr, Co, Cu, F, I, Mn, Mo, Se, Si, Sn, V and Zn • Even though they are present in REALLY small amounts, they are still essential to maintain homeostasis!

6. Atoms • Each element is made up of a single type of atom • The are the smallest units of matter that retain the properties of the element

7. Subatomic Particles • Protons (+) and Neutrons (0) are located in the nucleus of the atom • Electrons (-) move around in the space surrounding the nucleus • The number of protons in an atom equals the number of electrons, giving the atom a net charge of zero

8. Atomic Number – the number of protons • Atomic Mass – the number of protons plus the number of neutrons • Electron Shells – the area around a nucleus where you are most likely to find an electron

9. Ions • If an atom gives up or gains an electron it becomes an ion. • An ion is an atom that has a positive or negative charge due to unequal numbers of protons and electrons

10. Cation – a positive ion • Anion – a negative ion

11. Molecules • When 2 or more atoms share electrons, the resulting combination is called a molecule • May be 2 or more atoms of the same element (O2) or of different elements (H2O).

12. Molecular Formulas • A molecular formula indicates the type of and how many atoms are in a molecule • Ex – H2O means 2 hydrogen atoms and 1 oxygen atoms have joined

13. Compound • A molecule containing 2 or more atoms of different elements

14. Free Radical • An electrically charged ion or molecule that has an unpaired electron in its outermost shell • A free radical is unstable and destructive to nearby molecules • They break apart other molecules in the body by either giving up their unpaired electron or by taking an electron from another molecule.

15. Free Radicals in your Body… • Many processes in the body generate free radicals • Diseases associated with oxygen derived free radicals are cancer, artherosclerosis, Alzheimers, emphysema, diabetes, cataracts, macular degeneration, rheumatoid arthritis, and deterioration associated with aging.

16. Antioxidants • Substances that inactivate oxygen associated free radicals. • Consumption of antioxidants is though to slow the pace of damage caused by free radicals. • Dietary sources of antioxidants include selenium, beta-carotene and vitamins C and E. “The antioxidant will protect me…”

17. Chemical Bonds • Forces that bind the atoms of molecules together, resisting their separation. • Given the right conditions, two or more atoms can interact (bond) in such a way that a chemically stable arrangement of 8 valence (outer) electrons in each atom • 3 types of bonds: • Ionic • Covalent • Hydrogen (not really a bond if you talk to a chemist, but a REALLY strong attraction)

18. Ionic Bonds • The force of attraction between ions of opposite charges • This results from the transfer of electrons

19. Ionic bonds are found mainly in teeth and bones, most other ions in the body are dissolved in fluid.

20. Electrolytes • An ionic compound that breaks apart into cations and anions when dissolved is called an electrolyte because the resulting solution can conduct an electric current • Critical in controlling water movement, maintaining acid/base balance and producing nerve impulses

21. Covalent Bonds • Atoms form a molecule by sharing one, two or three pairs of electrons • These are the most common chemical bonds in the body

22. Polarity • If the neither atom in a covalent molecule has a greater attraction for electrons than the other the bond is said to be non-polar • Sometimes the electrons are not shared equally – one atom attracts the electrons more strongly than the other. This results in a polar bond

23. Polar Covalent Bonds • The sharing of electrons is unequal • The side of the molecule that attracts more electrons will have a partial negative charge (d-) while the side that does not have as many electrons will have a partial positive charge (d+) • The ENTIRE molecule is still NEUTRAL

25. Hydrogen Bonds • A VERY VERY strong interaction between some polar molecules containing hydrogen • A hydrogen atom in one molecule with a partial positive charge attracts a partial negative atom (F, O or N) from another molecule. • About 5% as strong as an actual covalent bond

27. Chemical Reactions • New bonds form and old bond are broken

28. Chemical Energy • Form of potential energy stored in chemical bonds • Breaking old bonds requires the input of energy, forming new bonds releases energy

29. Synthesis Reactions • Smaller molecules join to make larger molecules

30. Decomposition Reaction • Larger molecules are broken down into smaller molecules

31. Exchange Reactions • Consist of both synthesis and decomposition AB + CD  AD + BC

32. Reversible Reactions • Reactions that can proceed in either direction AB  A + B