1. I have 22 neutrons and a mass of 40.

2. I have 37 protons and 39 electrons.

3. I have 22 neutrons and 19 protons.

At your atom letter, you will finish your Bohr model of an atom. You will move around the room clockwise once finished to look at everyone else’s atoms. Record p+, no, e- for each.

Hyphen notation Nuclear Notation

Element – mass #

Uranium - 23823892 U

Topic: IsotopesTopic: Isotopes p. 35p. 35

Obj: understand the conclusions of Bohr’s nuclear atom. Use isotopic composition to calculate average atomic mass.

ESQ: How are isotopes similar? Different? How do you calculate the average atomic mass of an isotope?

All LIES!All LIES!

Dalton’s Atomic Theory – the part Dalton’s Atomic Theory – the part that states that atoms of the that states that atoms of the same element are identical same element are identical – is – is NOT always trueNOT always true

IsotopesIsotopes are atoms of the SAME are atoms of the SAME element that have element that have DIFFERENT DIFFERENT numbers of NEUTRONS numbers of NEUTRONS and and therefore different masses.therefore different masses.

Example:Example:There are 3 types of HydrogenThere are 3 types of Hydrogen

#p: #p: #p:#p: #p: #p:

#e: #e: #e: #e: #e: #e:

#n:#n: #n: #n: #n: #n:

Isotope NotationIsotope Notation

#1#1 - - Hyphen notation Hyphen notation

Element name – mass numberElement name – mass number

Ex 1: Ex 1: Nitrogen-15Nitrogen-15How many protons? How many protons? ____________

How many electrons? ______How many electrons? ______

How many neutrons? How many neutrons? ____________

77

8

2.) Nuclear Symbol 2.) Nuclear Symbol

Example 2: Example 2: 238238

9292

How many protons? How many protons? ____________

How many electrons? How many electrons? ____________

How many neutrons? How many neutrons? ____________

Isotope NotationIsotope Notation

U9292146

Name Symbol MassNumber

#p #n #e

Chlorine-37

35 Cl17

14C6

Carbon-12

37Cl 37 17 20 17

Chlorine-35 35 17 18 17

Carbon-14 14 6 8 612C 12 6 6 6

Get out page 34 homework por favor…

Put page 36 on the average atomic mass calculations.

On page 35 (notes), skip a line and put a subtitle: AVERAGE ATOMIC MASS

◦An oxygen atom weighs 2.657 x 10-22 g. This is difficult to use. Way too little!!!

◦The atomic mass unit (amu) was developed for the purpose of making calculations easier. It’s kind of like “mole.” We made up these units to make the numbers make more sense.

◦1 amu = 1/12th the mass of a Carbon-12 atom

The average atomic mass is a WEIGHTED average of ALL of the isotopes for an element.

The average atomic mass of a sample of an element can be found on the periodic table

◦Ex) Zinc = 65.39 amu

The mass of one atom is not exactly the same as the average mass of many.

◦Ex) 1 atom of Zinc 65.39 amu

for mass # p+ + no always equals a whole #

At Haltom, we average grades just like in math. Add up your grades and divide by the number of grades. This is a typical average.

Daily – 50% 63Major – 50% +74

137/2 = 68.5

In another school district, they calculate grades like this:

Daily grades – 40% 63Major grades – 60% 74

Here since they aren’t equal weights, the average is more influenced by the major grades since they count as a higher %.

This kid actually gets a 69.6 70 for the six weeks!

(% abundance x mass number isotope 1) + (% abundance x mass number isotope 2) + (% abundance x mass number isotope 3) + etc. = average atomic mass for the element

DO NOT DIVIDE BY ANYTHING! This is not a regular average. Don’t forget to change the percentage to a decimal first!!!

means how often it is found

Copper has two naturally occurring isotopes: copper-63 (69.17%) and

copper-65 (30.83%).

Calculate the average atomic mass of copper if the relative masses of the isotope are copper 63 (62.93 amu) and

copper-65 (64.93 amu).

Cu-63 (0.6917 x 62.93 amu) Cu-65 + (0.3083 x 64.93 amu) 1)Change % to a decimal2)Line up your info.3)Use parentheses on calculator if you want to do

it all at once without having to write it down for each isotope! May try to do it without them and check the order of operations. Some calculators know how to make this work even without the parentheses.

Cu-63 (0.6917 x 62.93 amu) Cu-65 + (0.3083 x 64.93 amu)

Avg. mass = 63.55 amu

*Notice average is always between the low & high amu but not necessarily in the middle.

Naturally occurring boron is 80.20% boron-11 (atomic mass = 11.01 amu) and 19.80% of some other isotopic form of boron. What must the atomic mass of this second isotope be in order to account for the 10.81amu average atomic mass of boron? Round to the nearest hundredth.

Naturally occurring boron is 80.20% boron-11 (atomic mass = 11.01 amu) and 19.80% of some other isotopic form of boron. What must the atomic mass of this second isotope be in order to account for the 10.81amu average atomic mass of boron? Round to the nearest hundredth.

1. Gold2. Tin3. Arsenic4. Lead5. Beryllium6. Bromine7. Potassium8. Chlorine9. Sodium10. Manganese

11.Ag12.Hg13.U14.Fe15.Cr16.I17.Pt18.Cu19.P20.He

An unknown element, Q, has an average atomic mass of 73.75 amu. The first isotope of Q has a mass of 72.99 amu and the second isotope has a mass of 74.99 amu. What are the percentages of each isotope?

Remember… X 1-x

Watch Sig Figs!!!

Open the container and I will hurt you… F!!!!