1. The Nuclear Atom Atoms differ from one another by their number of: 1.Protons 2.Neutrons 3.Electrons Electrons have a NEGATIVE charge. The MASS of an electron is 1/1840 less massive than either a proton or a neutron. The ELECTRONS in an atom are responsible for the chemical properties of the element.

2. The Nuclear Atom The nucleus contains PROTONS and NEUTRONS. Protons and neutrons have the same mass 1.66 x 10 -24 g (actual) 1 (relative) Protons are POSITIVE Neutrons are NEUTRAL

3. The Nuclear Atom In a NEUTRAL atom, the number of protons = number of electrons. Determine the number of electron in a neutral atom that has 13 protons. 13

4. The Nuclear Atom The identity of an atom is determined by the number of PROTONS. The number of PROTONS in an element is represented by the ATOMIC NUMBER The numbers of NEUTRONS and PROTONS in an element are represented by the MASS NUMBER The PROTONS and NEUTRONS make up the mass of an atom and are responsible for the stability of the atom.

5. What is an isotope? An isotope is an atom with the same number of protons, but different numbers of neutrons. Every atom is considered an isotope.

6. The Nuclear Atom Standard Nuclear Notation is used to represent each isotope in existence. X A Z X = element symbol A = Mass Number Z = Atomic Number

7. The Nuclear Atom Example 1: Write the symbol for the atom that has an atomic number of 9 and a mass number of 19. F 19 9 How many protons, neutrons and electrons does this atom have? PROTONS = 9 NEUTRONS = 10 ELECTRONS = 9

8. The Nuclear Atom The atomic masses of elements are calculated from EVERY STABLE ISOTOPE of the element. Calculating the AVERAGE ATOMIC MASS: Atomic Mass Unit- Defined as 1/12 the mass of ONE atom of CARBON – 12 (1.66 x 10 -24 g). The mass of each element is a weighted average of the isotopes of the element.

9. Isotope Example Calculate the following: –Jodi scored the following grades: Homework: 100,70,100 Quizzes: 98,88,72 Tests: 62 What is Jodi’s average?

10. Isotope Example Calculate the following: –Jodi scored the following grades: Homework: 100,70,100 Quizzes: 98,88,72 Tests: 62 What is Jodi’s average if homework counts 20%, quizzes count 30% and tests count 50%?

11. Isotope Example # MuffinsMass(g)% Abundance Mass contribution 225.6 127.9 325.2 Calculate the following: –Khori has 6 blueberry muffins. The muffins have the following masses:

12. The Nuclear Atom Example 1: Silicon has three stable isotopes. The following information is available for the three isotopes: IsotopeMass (amu)Fractional Abundance (%) Silicon – 2827.97792.21 Silicon – 2928.9764.70 Silicon – 3029.9743.09 (27.977 amu · 0.9221) + (28.976 amu · 0.0470) + (29.974 amu · 0.0309) = 28.09 amu

13. The Nuclear Atom Example 1: Iron has four stable isotopes. The following information is available for the four isotopes: IsotopeMass (amu)Fractional Abundance (%) Iron – 5453.93961275.845 Iron – 56 55.9349393 91.754 Iron - 5756.93539582.119 Iron - 5857.93327730.282 = 55.85 amu