Unit 2/B: Chemical Interactions

1. Unit 2/B: Chemical Interactions Chapter 5: Atomic Structure and the Periodic Table Chapter 6: Chemical Bonds and Compounds Chapter 7: Chemical Reactions Chapter 8: Solutions Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

2. Chapter 5: Atomic Structure and the Periodic Table A substance’s atomic structure determines its physical and chemical properties 5.1 Atoms are the smallest form of elements 5.2 Elements make up the periodic table 5.3 The periodic table is a map of the elements Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

3. 5.1 Atoms are the smallest form of elements Before, you learned: All matter is made of atoms Elements are the simplest substances Now, you will learn: Where atoms are found and how they are named About the structure of atoms How ions are formed from atoms Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

4. All matter is made of atoms • Substances vary - How many different substances can there be? • 2400 years ago – Greek philosophers thought there were four basic substances – air, water, fire, and earth • Today – chemists know of about 100 basic substances, call elements, that account for everything we see and touch Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

5. Atoms in Earth’s Crust and Living Things Atoms of the element hydrogen account for about 90% of the total mass of the universe Hydrogen makes up only about 1% of the Earth’s crust – mostly in the form of water % by mass Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

6. Names and Symbols of Elements • Name Origin Examples: • Magnesium from the region in Greece, Magnesia • Lithium from Greek word lithos, “stone” • Neptunium named after planet Neptune • Einsteinium and Fermium named after scientists Albert Einstein and Enrico Fermi • Elements have a name and symbol • Hydrogen: H • Sulfer: S • Carbon: C • Aluminum: Al • Cadmium: Cd • Lead: Pb • Iron: Fe • Gold: Au (from aurum, Gold in Latin) Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

7. Each element is made of a different atom • Early 1800’s: British scientist John Dalton: • each element is made of tiny particles called atoms • All atoms of a particular element are identical, but are different from atoms of all other elements • Ex: the atoms of silver are different from an atoms of iron • Atoms cannot be divided into anything simpler • Not exactly true… Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

8. The Structure of an Atom • Atoms contain charged particles – either positive or negative • Positives repel positives • Negatives repel negatives • Positive and negative attract • Atoms – three types of particles: • Protons – positively charged • Neutron – uncharged • Electron – negatively charged • Protons and neutrons are • found in the nucleus of an atom • Are of similar mass • Electrons • move around the outside of the nucleus • Have a much smaller mass than protons or neutrons Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

9. Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

10. The Structure of an Atoms • Atoms are about 10-10m in diameter! • Millions of atoms are in the period at the end of a sentence • The electron cloud is actually 10,000 times the diameter of the nucleus! • But…electrons are bout 2000 times smaller than the protons or neutrons • Can never determine the exact location of an electron – always moving around • Negative attraction to the positive keeps electrons close to the nucleus, but away from each other • No electrical charge if # protons = # electrons Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

11. Atomic Numbers and Mass Numbers • All atoms are composed of the same particles… • Different numbers of protons in the nucleus • Atomic number = # protons in the nucleus • Atomic mass number = # protons + # neutrons • Same elements have same # protons but not always the same # neutrons, so may have different atomic masses • Ex: Chlorine atoms have 17 protons, some have 18 neutrons, some have 20 neutrons = Chlorine isotopes • Isotopes: atoms of the same element that have a different number of neutrons • Chlorine-35, Chlorine-37 • # protons? # neutrons? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

12. Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

13. Atoms form ions • If # protons = # electrons  no electrical charge • Ion: formed when an atom loses or gains one or more electrons • What if an atoms loses a proton? Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

14. Formation of Positive Ions • If the atoms loses one electron, the charges are no longer balanced: one more proton than electrons • Size is different: fewer electrons, less repulsion • Lose one electron: X+, lose two electrons: X2+ Ex: Na+, Ca2+ Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties

15. Formation of Negative Ions • If the atoms gain one electron, the charges are no longer balanced: one less proton than electrons • Size is different: more electrons, more repulsion • Gain one electron: X-, gain two electrons: X2- Ex: Cl-, O2- Atomic Structure and the Periodic Table - A substance’s atomic structure determines its physical and chemical properties