1. Atomic Structure Mr. Matthew Totaro Legacy High School Chemistry 1

2. Experiencing Atoms Atoms are incredibly small, yet they compose everything. Atoms are the pieces of elements. Properties of the atoms determine the properties of the elements. 2

3. Experiencing Atoms There are about 91 elements found in nature. Over 20 have been made in laboratories. Each has its own, unique kind of atom. They have different structures. Therefore they have different properties. 3

4. The Nuclear Atomic Model 4

5. Atomic Theory from 1800-1911 5

6. The Modern Atom Atoms are composed of three main pieces: Protons (+), Neutrons (neutral), and Electrons (-). The nucleus contains protons and neutrons. The electrons move outside the nucleus The radius of the atom is about 10 5 times larger than the radius of the nucleus. 6

7. Subatomic Particles Protons and electrons are the only particles that have a charge. Protons and neutrons have essentially the same mass. The mass of an electron is so small we ignore it. 7

8. The Sub-Atomic Particles 8

9. 9 Elements Each element has a unique name and symbol. The symbol is either one or two letters  One capital letter or one capital letter + one lower case letter.  H = Hydrogen = “water-former”  Br = Bromine = ‘stench’ Liquid Bromine

10. Atomic number = number of protons in nucleus Mass number = number of protons + number of neutrons = atomic number + number of neutrons 2.3 10

11. Example 2.3b How many protons, electrons, and neutrons are in an atom of ? for most stable isotopes, n 0 > p + Check: Z = 24 = # p + # e - = # p + = 24 Solution: in neutral atom, # p + = # e - mass number = # p + + # n 0 Concept Plan: Relationships: therefore A = 52, Z = 24 # p +, # e -, # n 0 Given: Find: symbol atomic number # p + # e - symbol atomic & mass numbers # n 0 A = Z + # n 0 52 = 24 + # n 0 28 = # n 0 11

12. Isotopes: Atoms of the same element with different masses. Isotopes have different numbers of neutrons. 12

13. Ions Cation – ion with a positive charge - When a neutral atom loses one or more electrons Anion – ion with a negative charge -When a neutral atom gains one or more electrons Na 11 protons 11 electrons Na + 11 protons 10 electrons Cl 17 protons 17 electrons Cl - 17 protons 18 electrons 2.5 13

14. 13 protons, 10 (13 – 3) electrons, 14 neutrons 34 protons, 36 (34 + 2) electrons, 44 neutrons Do You Understand Ions? 2.5 How many p +, n 0, and electrons are in?Al 27 13 3+ How many p +, n 0, and electrons are in?Se 78 34 2- 14

15. Review What is the atomic number of boron, B? What is the atomic mass of silicon, Si? How many protons does a chlorine atom have? How many electrons does a neutral neon atom have? Will an atom with 6 protons, 6 neutrons, and 6 electrons be electrically neutral? Will an atom with 27 protons, 32 neutrons, and 27 electrons be electrically neutral? Will an Na atom with 10 electrons be electrically neutral? 15

16. Review What is the atomic number of boron, B? 5 What is the atomic mass of silicon, Si? 28.09 amu How many protons does a chlorine atom have? 17 How many electrons does a neutral neon atom have? 10 Will an atom with 6 protons, 6 neutrons and 6 electrons be electrically neutral? Yes Will an atom with 27 protons, 32 neutrons, and 27 electrons be electrically neutral? Yes Will an Na atom with 10 electrons be electrically neutral? No 16