1. Warm up 9-30-08 What part of the atom has a positive charge and where is it found?

2. the atom  What is an atom?  What are the parts of an atom?  What is the structure of the atom? The smallest particle of an element that has the characteristics of that element protons (p+); neutrons (n); electrons (e-) Nucleus contains protons & neutrons, electrons circle the nucleus in an electron cloud n e- P+ n

3. something to think about We all know that “opposites attract” and “like charges repel” –SO: If electrons are negatively charged and protons are positively charged, why don’t the electrons fall into the nucleus? ?

4. Niels Bohr proposed a model in which the electrons would stably occupy fixed energy levels around the nucleus, known as orbitals. Each orbital has a limited capacity for electrons. something to think about

5.  Some elements also have neutrons  Neutrons have no charge  They are in the nuclei of atoms  The element also has the same number of electrons  Electrons have negative charge  Change the number of electrons  charge the atom  Each element in the Periodic Table has a different number of protons in its nucleus  Protons have positive charge  Change the number of protons  change elements e- Recipe for an atom P+ n

6. Atomic number Atomic weight Name Symbol Protons = 8Electrons = 816 – 8 = 8 neutrons

7. # Protons = # Electrons The electron orbitals # Neutrons = Atomic Weight – Atomic #

8. # Protons = # Electrons # Neutrons = Atomic Weight – Atomic #

9. Shell structure activity Carbon = C Sulfur = S Neon =Ne Chlorine = Cl How many protons and electrons do these elements have? Draw the electron shell structure for each. 3 protons 3 electrons 4 neutrons e e e n n n p p p n

10. Navigating the Periodic Table  The columns are the “groups”  Each group has similar chemical properties  The groups are numbered starting with 1 at the left  Elements with similar properties have the same number of electrons in the outermost shell  The rows are the “periods”  Each period starts a new shell of electrons  The periods are numbered starting with 1 at the top

11. Atoms, Elements and Compounds  Compound: a collection of 2 or more different atoms, bound together.  H 2 O or CO 2  Atom: smallest unit of an element  Element: any of more than 100 fundamental substances that consist of atoms of only one kind (C; K; Mg; Ca)

12. The mighty electron e e e e e e 6P 6N Carbon e e e e e e 6P 12P 12N e e e e e e e e e e e e 6P 10P 10N e e e e neon magnesium e e e e e e 6P 17P 17N e e e e e e e e e e e chlorine 17 34 Cl

13. e e e e e e e 6P 17P 17N e e e e e e e e e e e e e e e e e 6P 17P 17N e e e e e e e e Cl - e e e e e e 6P 17P 17N e e e e e e e e e e 6P 11P 11N e e e e e Na + Opposites attract Ionic bond

14. CHARGE!!!  Ion – an atom with a charge  Cation – an atom with a positive charge  less electrons than protons  Anion – an atom with a negative charge  More electrons than protons Na+ Cl -

15. covalent bond: When electrons are SHARED e e e 6P 17P 17N e e e e e e e 6P 8P 8N e e O 1P H H e e e e

16.  Molecule – a group of atoms held together by covalent bonds H 2 O MOLECULES  Chemical reactions occur when bonds between atoms are formed or broken