Day 5 Chapter 4 Section 2 and 3

Daily Problems (5) Introduction: What makes up the mass number? Draw and label the subatomic particles of an atom. Charges. Which particles account for most of an atom’s mass? What does it mean to be electrically neutral? Using your drawing identify the particles found in the nucleus. What is the charge of the nucleus? If an atom is said to have a 3- charge what does that indicate? 3+ charge?

How atoms differ Start with some Vocab Atomic Number Atoms total # of Protons Atoms Total # of Electrons Note: as long as the atom is neutral in charge Atomic # identifies an atom of a particular element. IT NEVER CHANGES!!!! How to read the Periodic Table

Check Identify the following to fill in the chart. Name of element # of Protons Average Atomic Mass

Atomic numbers Composition of Several Elements Element Atomic Number Complete the following table Composition of Several Elements Element Atomic Number Protons Electrons a. Pb 82 b. 8 c. 30 82 82 O 8 8 Zn 30 30

Isotopes and Mass number What do we know…? Does the # of protons of an element ever Change? NO Does the # of electrons of an element ever change? What’s Left? # of Neutrons will change What does this mean? Atoms with the same number of protons but different number of neutrons are called “ISOTOPES”.

The mass number What makes up the mass number of an isotope. Remember Relative Mass Protons = 1amu Neutrons = 1amu What’s this mean? If an element has 1 proton and 1 neutron what's the Mass Number? 2 So…The Mass Number is… (Atomic #) + (# of neutrons)

What does all this mean? Elements have different forms in nature Lets look at Copper… How many protons in Copper? 29 protons Does this ever change? No But copper has two forms with different mass numbers. What changes…# of Protons or # of Neutrons? # of neutrons

Copper - isotopes Cu Cu Copper – 63 Copper - 65 Other ways to write it Mass number Other ways to write it Cu 63 29 Cu 65 29

Learning check # 1 Potassium – 39 Potassium – 40 Potassium - 41 Protons Neutrons Electrons 19 20 19 21 19 22 19 19 19 _____e- _____e- _____e- 19 19 19 _____p+ _____n _____p+ _____n _____p+ _____n 21 22 23 Now Write it! 39 19 40 19 41 19 K K K

Learning Check #2 Fill in the Chart Isotope Composition Data Element Atomic # Mass # Protons Neutrons electrons Symbol Neon 10 22 Calcium 20 46 Ca Oxygen 8 17 Iron 26 57 Zinc 30 64 Mercury 80 204 An atom has a mass number of 55. Its number of neutrons is the some of its atomic number and five. How many protons, neutrons and electrons does this atom have? What is the identity of this atom? 30 neutrons, 25 protons, 25 electrons Magnesium

Natural abundance In nature, elements are a combination of isotopes. So, if the mass of Neon is the combination of all three isotopes, how do you calculate the atomic mass?

(Mass #1) (%) + (Mass #2) (%) + (Mass #3) (%)… = AMU Natural abundance Keep it simple… Multiple the % (decimal form) by each mass. Then add them together. This will give you the Atomic Mass Unit (amu) (Mass of isotope #1) (% decimal) (Mass #1) (%) + (Mass #2) (%) + (Mass #3) (%)… = AMU

Learning check #3 Three magnesium isotopes have atomic masses and relative abundances of 23.985amu (79.99%), 34.986 amu (10.00%), and 25.982 amu (11.01%). Calculate the atomic mass of magnesium. Follow your rules. 23.985 (.7999) + 34.986 (.1000) + 25.982 (.1101) = 25.545 Nitrogen has two naturally occurring isotopes, N-14 & N- 15. Its atomic mass is 14.001. Which isotope is more abundant? Common Sense! N – 14 : it’s closest to the atomic mass

Homework assignment Problems: , 39, 42, 46, 48, 58-62, 64

a look ahead Day 6: Isotope Lab / Quiz on the Atom Day 7: Chapter 4 Section ¾ Day 8: Isotopes Quiz: Chapter 24 Section 1 Day 9: Chapter 24 Section 2