1. 2.1 Atoms, Ions, and Molecules KEY CONCEPT All living things are based on atoms and their interactions.

2. 2.1 Atoms, Ions, and Molecules Living things consist of atoms of different elements. Atom: the smallest basic unit of matter. Element: one type of atom Ex.: carbon, hydrogen H O Element 1: Hydrogen atom (H) Element 2: Oxygen atom (O) Outermost Energy Level: electrons here determine how atoms form ions or form covalent bonds. 1. electron (-) 2. nucleus Composed of: 3. protons 4. neutrons

3. 2.1 Atoms, Ions, and Molecules –The nucleus contains protons and neutrons. –An energy level is an area around a nucleus in which electrons are located. Oxygen atom (O) Nucleus: 8 protons (+) 8 neutrons outermost energy level: 6 electrons (-) inner energy level: 2 electrons (-) An atom has a nucleus and electrons.

4. 2.1 Atoms, Ions, and Molecules –Ex: water (H 2 O) O HH _ ++ A compound is made of atoms of different elements bonded together.

5. 2.1 Atoms, Ions, and Molecules –EX: carbon dioxide (CO 2 ) A compound is made of atoms of different elements bonded together. –water (H 2 O)

6. 2.1 Atoms, Ions, and Molecules –Ex: many other carbon-based compounds (macromolecules) in living things A compound is made of atoms of different elements bonded together. –water (H 2 O) –carbon dioxide (CO 2 )

7. 2.1 Atoms, Ions, and Molecules STOP & REVIEW All living things are based on _________ and their __________________. An ______________ is the smallest basic unit of matter. A ____________ is made of atoms of different elements bonded together. EX: _____________, _________, and ______________________.

8. 2.1 Atoms, Ions, and Molecules STOP & REVIEW ANSWERS All living things are based on __atoms_______ and their _____interactions_____________. An ____atom__________ is the smallest basic unit of matter. A ___compound_________ is made of atoms of different elements bonded together. EX: __water___________, __carbon dioxide_______, and __carbon based macromolecules____________________.

9. 2.1 Atoms, Ions, and Molecules Ions form when atoms gain or lose electrons. –positive ions: formed when atoms lose electrons. Ex.: Na + –negative ions: formed when atoms gain electrons. Ex.: Cl - Sodium atom (Na)Chlorine atom (CI)Sodium ion (Na + )Chloride ion (CI - ) Na loses an electron to CI ionic bond gained electron

10. 2.1 Atoms, Ions, and Molecules Ions form when atoms gain or lose electrons. Ionic bonds form between oppositely charged ions due to electrical attraction.

11. 2.1 Atoms, Ions, and Molecules Atoms share pairs of electrons in covalent bonds. A covalent bond forms when atoms share a pair of electrons. Molecule: atoms bonded together by covalent bonds; not necessarily a compound. Ex.: O 2, H 2 O covalent bonds Oxygen atom (O)Carbon atom (C)Oxygen atom (O) Carbon dioxide (CO 2 )

12. 2.1 Atoms, Ions, and Molecules STOP & REVIEW An _________ is an atom that has gained or lost one or more electrons. ___________________ form between oppositely charged ions due to electrical attraction. A ____________________ forms when atoms share a pair of electrons

13. 2.1 Atoms, Ions, and Molecules STOP & REVIEW ANSWERS An __ion_______ is an atom that has gained or lost one or more electrons. _____ionic bond______________ form between oppositely charged ions due to electrical attraction. A ___covalent bond_________________ forms when atoms share a pair of electrons

14. 2.1 Atoms, Ions, and Molecules TED-ED Video http://ed.ted.com/lessons/just-how-small-is-an-atom