1. The Atom

2. What are Atoms? Atoms are the basic building blocks of matter that make up everyday objects. Ex. (chairs, air, You!) Made up of a nucleus and an electron cloud The smallest particle of an element that keeps the properties of an element. How small is an atom? World population 7 000 000 000 Atoms in a penny 29 000 000 000 000 000 000 000

3. ParticleChargeMass #Location Electron0Electron cloud Proton+11Nucleus Neutron01Nucleus

4. The negative (-) particle is called an Electron Discovered by J.J. Thomson Basis of televisions!

5. The positive (+) particle is called a Proton Discovered by Ernest Rutherford in famous “Gold Foil” experiment Found in the nucleus +

6. The neutral (no charge ) particle is called a Neutron Discovered by James Chadwick Also found in the nucleus No charge

7. Structure of an Atom The nucleus is a tiny dense region centrally located in the atom surrounded by an electron cloud. - How dense is it? - How small is it? An atom is made up of mostly empty space! If the nucleus was the size of this dot it would weigh as much as 70 cars! If the nucleus was the size of a football the electrons would be about 2 miles away!

8. Atomic Number Number of protons in an atom Identifies the element All atoms of an element have the same number of protons

9. Atomic Number on the Periodic Table 11 Na Symbol Atomic Number

10. Learning Check Element/NameAtomic #Proton # Ca/Calcium20 O/Oxygen 16 Ag/Silver 30

11. A certain atom has a nucleus containing six protons and eight neutrons and has six electrons orbiting the nucleus. This atom is a form of the element — A silicon B carbon C magnesium D calcium TEST QUESTION

12. State the number of protons for atoms of each of the following 1. Nitrogen A) 5 protons B) 7 protons C) 14 protons 2. Sulfur A) 32 protons B) 16 protons C) 6 protons 3. Barium A) 137 protons B) 81 protons C) 56 protons Learning Check

13. The picture shows a model of the element — A fluorine B helium C beryllium D oxygen TEST QUESTION

14. Number of protons and neutrons in an atom. mass number = protons + neutrons Mass Number

15. The atomic symbol shows the mass number and the atomic number. Symbol for Sodium: mass number 23 Na atomic number 11 Atomic Symbols

16. Atomic Mass on the Periodic Table 11 Na 22.99 Atomic Number Symbol Atomic Mass

18. Atomic Mass Number ElementMass #Proton #Neutron # Li 12 K 16 Na

19. Isotopes Atoms of the same element (same atomic number) with different mass numbers (different number of neutrons). An element may have different numbers of neutrons, but NOT different numbers of protons. Isotopes of chlorine 35 Cl 37 Cl17 chlorine - 35 chlorine - 37

20. Learning Check 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 _______ _______ _______

22. Atomic Mass The mass shown in the periodic table is the mass of the element as its occurs naturally. If the element has more than one isotope, the mass shown is the weighted average of the masses of the isotopes. Mg has 3 isotopes. 24 Mg 78.99% 23.985 amu 25 Mg 10.00% 24.986 amu 26 Mg 11.01% 25.983 amu weighted average of Mg: 0.7899x23.985 18.946 0.1000x24.986 2.499 0.1101x25.983+2.861 24.31 amu atomic weight of Mg based on natural abundance: 24.31 amu