YOU WILL NEED: –CALCULATOR –NOTEBOOK –PERIODIC TABLE

Robert Millikan He measured the charge of an electron. Using this he gave a negative charge to oil droplets and was able to measure how different charged plates changed the droplets rate of fall. This also allowed him to measure the mass from the charge to mass ratio. hill.com/sites/ /student_view0/chapte r2/animations_center.html#

Robert Millikan He measured the charge of an electron. Using this he gave a negative charge to oil droplets and was able to measure how different charged plates changed the droplets rate of fall. This also allowed him to measure the mass from the charge to mass ratio. hill.com/sites/ /student_view0/chapte r2/animations_center.html#

Comparison of Atomic Models Dalton’s Model Thomson’s Model Rutherford’s Model

Learning Target Know the differences between electrons, protons, and neutrons. Determine the number of electrons and protons in a neutral atom and ion.

Atom Comparisons VS.

Electrons (negative) charge, have a mass of close to zero or negligible Protons (positive) are bigger than electrons. The part of an atom that gives an element its identity. Neutrons (neutral) are slightly bigger in mass than a proton.

Every element has a unique atomic number which is equal to the number of protons. Elements atomic number is just above the chemical symbol on periodic table. The individual atom is electrically neutral- means number of protons always equal number of electrons.

How many protons and electrons in the following atoms: 1. Na 2. Pb 3. Os

Ions Ions are atoms that have lost or gained one or more electrons giving them a positive or negative charge!

If an ion looses an election it has a positive charge. If an ion gains an electron it has a negative charge.

How many protons and electrons does a magnesium atom have? What will the charge be if it loses 2 electrons? No. of protons -12 (+) No. of electrons - 10 (-) Charge of Ion 2+ Write it like this: Mg 2+

19. Cu² F Ion Protons Electrons 27 10

Learning Target Know how the atomic masses on the periodic table are calculated using the isotopes of the element. Know how to determine the number of protons, neutrons and electron in an atom or ion.

ParticleLocation Charge(C)Mass (g)Mass (amu) ProtonInside nucleus x x = 1 Neutron Inside nucleus x = 1 Electron Outside nucleus x x = 0

Atomic Mass Units (amu): roughly equal to the mass of a proton or neutron. **the mass of an atom is measured in amu’s 1 amu = 1.66x g

VS.

Isotopes Isotopes are atoms that have the same number of protons but different numbers of neutrons In nature, elements are almost always found as a mixture of isotopes

Penny Isotopes Analogy the pennies are different atoms of the element penny (Pe).

Step #1 Mass of pennies 1. Record the total number of pennies in your container. 2. Separate your penny atoms into 2 categories: and earlier 2. Later than In 2 data tables (1 for pre-1982 and 1 for post-1982) record the year and mass of each individual penny. Some years may be duplicated – record each penny individually.

Step #2 Averages Calculate the average mass of the pennies in your sample that are 1982 or earlier. This is isotope #1 Calculate the average mass of the pennies in your sample that are post This is isotope #2

Step #3 Percentages Calculate the percentage of pennies that are pre1982 pennies in your container. Calculate the percentage of pennies that are post 1982 in your container. **KEEP THESE IN DECIMAL FORM. (0.47 not 47%)

Step #4 Calculate the Average Atomic Mass Use the formula: Average Atomic Mass = (decimal % of 1 st Isotope x Average Mass of 1 st Isotope) + (% of 2 nd Isotope x Average Mass of 2 nd Isotope) *Use decimal form of percentage in calculation..50 not 50%

Atomic mass Atomic Number/ number of protons Atomic mass: weighted average of the masses of the existing isotopes of an element.

To identify an isotope more specifically, chemists add a number after the elements name. ex. Carbon-11 Carbon-12 Carbon-14 This number is called the isotope’s mass number and is the sum of the isotope’s number of protons and neutrons. Which of the 3 isotopes of Carbon is the most abundant?

Differences between isotopes? What are the differences between isotopes of the same element? Isotopes react in the same way as others of the same element Do you think that two different isotopes of the same element react the same way? Yes they react the same way.

HOW ARE PENNIES AN ANALOGY FOR ISOTOPES? What was Dalton’s 2 nd Postulate? (page 92) Was it correct? Hmmm

Complete Chemical Symbols Mass number Atomic number Charge Ba 2+ Number of protons = Atomic # Number of neutrons = Mass # - Atomic # Charge = Atomic # – Number of electrons

Complete the Table Chemical Symbol No. of Protons No. of Electrons No. of Neutrons Atom or Ion? 38 Sr Atom 90

YOU WILL NEED: –CALCULATOR –NOTEBOOK –PERIODIC TABLE –3-3 Apply Worksheet

WARM UP What is the atomic mass unit of a proton? Neutron? Electron? What is the atomic mass of an element represent?

Practice What is the chemical symbol for the ion with 13 protons and 10 electrons? What is the chemical symbol for the ion with 7 protons and 10 electrons? How many protons and electrons are present in the S 2- ion? How many protons and electrons in Li + ion?

Mass Number – the sum of an isotope’s protons and neutrons. To name an isotope using chemical symbols, simply place the atom’s mass number to the upper left of the element symbol. For example 37 Cl.

Complete the Table Chemical Symbol No. of Protons No. of Electrons No. of Neutrons Atom or Ion? 38 Sr Atom 90