Exploring Atoms, Elements & Compounds

1. What’s the MATTER? Anything that has massand takes up space What about air ….

2. Slice and dice it to as small a piece you can make it…….. atom

3. Electroncloud 6e– + + Nucleus 6 + Protons Massnumber = 12 6 Neutrons – 6 Electrons An atomhas a positively charged center surrounded by a negatively charged area. + -

4. Electron cloud – – 2e– + + + + Nucleus + Protons 2 Massnumber = 4 Neutrons 2 – Electrons 2 0 3 subatomic particles….. 2 regions 1. nucleus(positiive region) protons (positive) and neutrons (neutral) 2. electron clouds (negative region) electrons (negative)

5. protons Electrons(-) neutrons p.p.p.p.p.pppositive It’s electric … no thanks.. NEUTRAL PP ….. Ewe….

6. Atoms and Elements

7. 0 ELEMENTS, ATOMS, AND MOLECULES • Living organisms are composed of about 25 chemical elements • About 25 different chemical elements • Are essential to life • About 90 naturally occurring elements • Listed on the periodic table with some unnatural ones

8. How many different naturally occuring elements are there? • About 25 • About 90 • Over 1000

10. Atoms and Elements • Horizontal rows are called periods. • Vertical columns are called groups.

11. 0 • Differences in Elements • Atoms of each element • Are distinguished by a specific number of protons 0

12. IRON Atomic number Symbol Atomic mass

13. IRON Atomic Mass ------ 56 Atomic number ------- 26 Protons -------- 26 Neutrons -------- 30 Electrons -------- 26

14. 0 • Carbon, hydrogen, oxygen, and nitrogen • Make up the bulk of living matter

15. 0 • Trace elements are common additives to food and water • Dietary deficiencies in trace elements • Can cause various physiological conditions

16. 0 • Trace elements are essential to human health • And may be added to food or water

17. Which elements are the most common in living things? • Carbon, Helium, Chlorine and Sulfur • Hydrogen, Carbon, Nitrogen and Calcium • Carbon, Oxygen, Nitrogen and Hydrogen

18. What’s makes gold gold and lead lead? • The number of protons • The number of neutrons • The number of electron

19. 0 • Isotopes • The number of neutrons in an atom may vary • Variant forms of an element are called isotopes • Some isotopes are radioactive Table 2.4

20. Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Electron Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8 Hydrogen (H) Atomic number = 1 Carbon (C) Atomic number = 6 0 • Electron arrangement determines the chemical properties of an atom

21. 0 • Atoms whose shells are not full • Tend to interact with other atoms and gain, lose, or share electrons • These interactions • Form chemical bonds

22. Why do atoms form bonds to make molecules? • To gather more protons for their nuclei • To increase the number of their electrons • To have a stable number of electrons in their outermost shell

23. Sodium Chlorine Sodium Chloride 0 Elements can combine to form compounds • Chemical elements • Combine in fixed ratios to form compounds • Millions of different molecules possible

24. MATTER atom element Pure substance can be found in nature • Pure substance formed when two or more different elements combine. compound molecule

25. molecules _ O H H + +

26. – + Transfer of electron – – Cl Na Cl Na ClChlorine atom NaSodium atom Cl–Chloride ion Na+Sodium ion Sodium chloride (NaCl) 0 • Ionic bonds are attractions between ions of opposite charge • When atoms gain or lose electrons • Charged atoms called ions are created

27. – + Transfer of electron – – Cl Na Cl Na ClChlorine atom NaSodium atom Cl–Chloride ion Na+Sodium ion Sodium chloride (NaCl) 0 • An electrical attraction between ions with opposite charges • Results in an ionic bond

28. Na+ Cl– 0 • Sodium and chloride ions • Bond to form sodium chloride, common table salt

29. Ionic Bonding

30. covalent bonds Oxygen atom (O) Carbon atom (C) Oxygen atom (O) Carbon dioxide (CO2 ) 0 • Covalent bonds join atoms into molecules through electron sharing

31. 0 Molecules can be represented in many ways

32. (–) (–) O H H (+) (+) 0 • Unequal electron sharing creates polar molecules • A molecule is nonpolar • When its covalently bonded atoms share electrons equally

33. (–) (–) O H H (+) (+) 0 • In a polar covalent bond • Electrons are shared unequally between atoms, creating a polar molecule Figure 2.9

34. (–) (–) O H H (+) (+) 0 • Hydrogen bonds are weak bonds important in the chemistry of life • The charged regions on water molecules • Are attracted to the oppositely charged regions on nearby molecules

35. (–) Hydrogen bond (+) H O (–) (+) H (+) (–) (–) (+) 0 • This attraction forms weak bonds • Called hydrogen bonds

36. 1. What type of bond is formed by sharing electrons? • Hydrogen • Covalent • Ionic

37. 2. What type of bond is very weak but important to holding together DNA? • Hydrogen • Covalent • Ionic

38. 3. What type of strong bond does salt make from sodium and chlorine? • Hydrogen • Covalent • Ionic

39. 4. Why do atoms of elements form chemical bonds with other atoms to form molecules? • To fill their nucleus with a stable number of protons • To fill the outer shell of their atoms with a stable number of electrons • To add to the number of neutrons in their nucleus

40. 5. Water is a molecule formed from Oxygen and 2 Hydrogen sharing electrons. What type of bond is this? • Covalent • Hydrogen • Ionic

41. 6. What makes each element unique is the number of protons it has in its nucleus. True or False

42. 7. Which type of chemical bonding is weakest? • Covalent • Ionic • Hydrogen