2. Elements, Atoms, and Ions Chemistry I: Chapter 2b Chemistry I Honors: Chapter 3 ICP: Chapter 17 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options> Print>UNcheck "Background Printing")!

3. The Language of Chemistry CHEMICAL ELEMENTS -CHEMICAL ELEMENTS - –pure substances that cannot be decomposed by ordinary means to other substances. Sodium Bromine Aluminum

4. The Language of Chemistry The elements, their names, and symbols are given on the PERIODIC TABLEThe elements, their names, and symbols are given on the PERIODIC TABLE How many elements are there?How many elements are there?

5. The Periodic Table Dmitri Mendeleev (1834 - 1907)

6. Glenn Seaborg (1912-1999 ) Discovered 8 new elements.Discovered 8 new elements. Only living person for whom an element was named.Only living person for whom an element was named.

7. An atom consists of a nucleusnucleus –(of protons and neutrons) electrons in space about the nucleus.electrons in space about the nucleus. The Atom Nucleus Electron cloud

8. Copper atoms on silica surface. An _____ is the smallest particle of an element that has the chemical properties of the element.An _____ is the smallest particle of an element that has the chemical properties of the element. Distance across = 1.8 nanometer (1.8 x 10 -9 m)

9. ATOM COMPOSITION protons and neutrons in the nucleus.protons and neutrons in the nucleus. the number of electrons is equal to the number of protons.the number of electrons is equal to the number of protons. electrons in space around the nucleus.electrons in space around the nucleus. extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water.extremely small. One teaspoon of water has 3 times as many atoms as the Atlantic Ocean has teaspoons of water. The atom is mostly empty space

10. ATOMIC COMPOSITION Protons (p + )Protons (p + ) –+ electrical charge –mass = 1.672623 x 10 -24 g –relative mass = 1.007 atomic mass units (amu) but we can round to 1 Electrons (e - )Electrons (e - ) – negative electrical charge –relative mass = 0.0005 amu but we can round to 0 Neutrons (n o )Neutrons (n o ) – no electrical charge –mass = 1.009 amu but we can round to 1

11. Atomic Number, Z All atoms of the same element have the same number of protons in the nucleus, Z 13 Al 26.981 Atomic number Atom symbol AVERAGE Atomic Mass

12. Mass Number, A C atom with 6 protons and 6 neutrons is the mass standardC atom with 6 protons and 6 neutrons is the mass standard = 12 atomic mass units= 12 atomic mass units Mass Number (A) = # protons + # neutronsMass Number (A) = # protons + # neutrons NOT on the periodic table…(it is the AVERAGE atomic mass on the table)NOT on the periodic table…(it is the AVERAGE atomic mass on the table) A boron atom can have A = 5 p + 5 n = 10 amuA boron atom can have A = 5 p + 5 n = 10 amu

13. Counting Protons, Neutrons, and Electrons Protons: Atomic Number (from periodic table) Neutrons: Mass Number minus the number of protons (mass number is protons and neutrons because the mass of electrons is negligible) Electrons: –If it’s an atom, the protons and electrons must be the SAME so that it is has a net charge of zero (equal numbers of + and -) –If it does NOT have an equal number of electrons, it is not an atom, it is an ION. For each negative charge, add an extra electron. For each positive charge, subtract an electron (Don’t add a proton!!! That changes the element!)

14. Learning Check – Counting Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12 C 13 C 14 C 6 6 6 #p + _______ _______ _______ #n o _______ _______ _______ #e - _______ _______ _______

15. Answers 12 C 13 C 14 C 6 6 6 #p + 6 6 6 #n o 6 7 8 #e - 6 6 6

16. Periods in the Periodic Table