Unit 5 lec 2- Subatomic particles What information would you get about an element from the periodic table?

The atomic number and mass are used to determine the number of protons, neutrons, and electrons in an atom

# of Protons = atomic number # of Neutrons = Mass number – atomic number this works because… Mass number = protons + neutrons, so if you take away the atomic number you are left with neutrons. # of Electrons = atomic number (for neutral atoms)

What is its atomic number and atomic mass? A bohr model of an atom. Notice the protons and neutrons in the nucleus and the electrons outside the nucleus s Which element is this? What is its atomic number and atomic mass?

For each symbol, specify the number of p,n,& e- Protons Neutrons Electrons 24He 2 612C 1735Cl 49Be

For each symbol, specify the number of p,n,& e- Protons Neutrons Electrons 24He 2 612C 6 1735Cl 17 18 49Be 4 5

Draw a Bohr model for an atom of each of the following Include where the protons, neutrons and electrons are located, include the proper number of protons, neutrons, and electrons, also identify the nucleus and electron clouds. Boron Flourine

Lewis dot structures Valence electrons – electrons in the highest occupied energy level/orbital of an atom Maximum of 8 valence electrons Use the periodic table to determine!

Why are valence electrons so important? Tells us the chemical properties of an element They are responsible for the formation and breaking of bonds

Lewis dot structures We use Lewis dot structures to show the number of valence electrons within an element

Draw Lewis dot structures for Carbon Sulfur Boron

Isotopes of Atoms: These are three isotopes of Hydrogen

4. What does the mass number tell you? 2. What structural characteristics do all three hydrogen atom isotopes have in common? 3. How does one isotope of hydrogen differ from another isotope of hydrogen? 4. What does the mass number tell you? 5. What does the atomic number tell you? 6. Define the term isotope.

Average Atomic Mass: Notice how the atomic masses are NOT whole numbers. (For example the atomic mass of sodium is 22.99 NOT 23). These are the average atomic masses for elements. This is a weighted average so more abundant (common) isotopes have a bigger effect than less abundant ones. Av. At.mass = ( percent abundance/100) mass A + ( percent abundance/100) mass B

Average Atomic Mass: 1. What if the teacher decided that test 1 would count for 40% of the final grade, test 2 would count for 35% of the final grade, and test 3 would count for 25% of the final grade. Calculate the new WEIGHTED AVERAGE for each student.

Average Atomic Mass: 1. What if the teacher decided that test 1 would count for 40% of the final grade, test 2 would count for 35% of the final grade, and test 3 would count for 25% of the final grade. Student A:     Student B:

Average Atomic Mass: 2. Suppose that student C had an average of 85. On each of his three tests he scored either 65 or 95. Which score occurred more often? EXPLAIN.

Now lets do this with isotopes in chemistry! 1. Neon has three different isotopes. 90.51% of neon atoms have a mass of 19.992 amu. 0.27% of neon atoms have a mass of 20.994 amu. 9.22% of neon atoms have a mss of 21.991 amu. What is the average atomic mass of neon? 2. Of all chlorine atoms, 75.771% are chlorine 35. Chlorine 35 atoms have a mass of 34.96855 amu. All other chlorine atoms are chlorine-37 with a mass of 36.96590. Calculate the average atomic mass of chlorine.

3. Calcium has three different isotopes. One has a mass of 35 3. Calcium has three different isotopes. One has a mass of 35.00 amu; another has a mass of 41.00 amu, and a third has a mass of 40.00 amu. Which isotope is most abundant of the three? (HINT: look at the periodic table). 4. An element exists with three isotopes. 24.1% have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu. What is the average atomic mass of this element? Using your periodic table identify which element this is.