Calculating the Average Atomic Mass Number Where did that decimal come from?

Slides:

Advertisements

Similar presentations

4.3: HOW ATOMS DIFFER ATOMIC NUMBER

Advertisements

Average Atomic Mass. How much does an atom weigh?  Protons & Neutrons:  1.67 X gram  Electrons:  9.10 X gram  To avoid working with.

AIM: HOW TO CALCULATE THE AVERAGE ATOMIC MASS? DO NOW:1. WHAT ARE THE 3 SUBATOMIC PARTICLES OF AN ATOM? LIST THE THREE SUBATOMIC PARTICLES AND THEIR CHARGE.

Average Atomic Mass.  An element can exist in a number of forms, called isotopes. Isotopes are forms of the same atom that vary in mass as a result of.

Average Atomic Mass.

1 Average Atomic Mass Chemistry Notes. 2 Relative Atomic Mass  Masses of atoms expressed in grams are very small, for example: One atom of Oxygen-16.

 Definition: Atoms of the same element that differ in their # of neutrons; therefore, they have different mass numbers.  Nearly every element has isotopes!

 Each element on the periodic table has an isotope.  What make an element have different isotopes?  There are 2 different isotopes of iron  Find the.

Average Atomic Mass. Average Atomic Mass – the weighted average of the masses of the isotopes of an element Every element is composed of several naturally.

Isotopes and Mass Number. Atomic Number The number of protons in each atom identifies it as an atom of a particular element Each atom has a unique number.

Atoms – a closer look at elements

Atomic Mass. Isotopes Reminder Yesterday we learned that the mass of all atoms of a certain element are not always the same –Some atoms may have more.

Mass Number Atomic Number equals the # of... NUCLEUS ELECTRONS PROTONS NEUTRONS NEGATIVE CHARGE POSITIVE CHARGE NEUTRAL CHARGE ATOM.

Isotopes and Weighted Averages

Isotopes Atoms of the same element that different mass numbers

Number of Protons = Number of Electrons Number of Protons = Atomic Number Atomic Mass = Protons + Neutrons.

Average Atomic Mass The weighted average of the masses of all the naturally occurring isotopes of an element.

Average Atomic Mass.

Isotopes  Atoms with the same number of protons but different numbers of neutrons  Ex) Carbon 12 vs. Carbon 14  These atoms have a different mass 

More about isotopes Atomic mass vs average atomic mass or atomic weight.

& Average Atomic Mass  Atoms with the same number of protons (they are the same element) but different number of neutrons.

Unit 3: Atomic Structure Atomic Mass Units (amu) and Calculating Atomic Mass.

Average Atomic Mass A different kind of average…

 Atomic Number- the number of protons in the nucleus of an atom of that element  Ex: Hydrogen atoms have only one proton in the nucleus, so the atomic.

Using Isotope Data to Find a Weighted Average.  Each isotope will have two values associated with it.  Mass of Isotope  Percent Abundance (% found.

Calculating the Average Atomic Mass. Steps for Calculating Average Atomic Mass (When given percentages of each isotope and each isotopes mass) 1. Convert.

…AND THE AVERAGE ATOMIC MASS Isotopes. PG 88 GENERAL- ATOMS OF THE SAME ELEMENT BUT HAVE DIFFERENT AMOUNTS OF NEUTRONS IN THE NUCLEUS PAGE 54 PRE AP ATOMS.

TAKE A …. GUIDED NOTES PAGE ATOMIC MASS W.S. ….OFF MY DESK.

Atomic Mass The Atomic Mass of Candium Lab. Atomic Mass This is the weighted average mass of the atoms in nature of that element A weighted avg mass reflects.

Section 4.3 How atoms differ. Atomic Number Represents three things in a neutral atom: 1. What element it is 2. The number of protons in each atom 3.

 The weighted average of its naturally occurring isotopes. Chemical Name Atomic # Chemical Symbol Atomic Mass (Average Atomic Mass)

Average atomic Mass. What does the atomic mass tell us on the Periodic table?

Chapter 3 Average Atomic Mass. Section 3 Counting Atoms Relative Atomic Masses The standard used by scientists to compare units of atomic mass is the.

Average Atomic Mass. Relative Atomic Masses  Masses of atoms (in grams) are very small, so for convenience we use relative masses.  Carbon-12 is our.

Determining Average Atomic Mass

What is average atomic mass?

Average Atomic Mass.   atomic masses reported in periodic table represent: weighted average of masses of all naturally occurring isotopes of an element.

Average Atomic Mass What is average atomic mass? Average atomic mass is the weighted average of the atomic masses of the naturally occurring isotopes of.

Atomic Mass. Atomic mass Most of the mass of an atom is in the nucleus. Most of the mass of an atom is in the nucleus. The nucleus is where all of the.

Chapter 4 AVERAGE ATOMIC MASS. Atomic Mass… n The weighted average of the masses of all the naturally occurring isotopes of that element. n Is not a whole.

Atomic Structure. Subatomic Particles In the nucleus: Protons Mass  1 amu Charge = +1 Neutrons Mass  1 amu Charge = 0 In the electron cloud: Electrons.

Atomic Structure Chapter 4. Sizing up the Atom O Radii of most atoms: 5 x m to 2 x m O Copper penny contains 2.4 x atoms. The population.

Isotopic Abundance Pages Thinking question Why are there decimal places for atomic masses on the periodic table if protons and neutrons have amu.

Isotope Atoms that have the same number of p +, but different numbers of n o.

WEIGHTED AVERAGE MASS NUMBER: 1)The mass number on the periodic table is calculated from the weighted average of the most abundant isotopes. 2) Abundance.

Average Atomic Mass ► Average Atomic Mass – the weighted average of the masses of the isotopes of an element ► Every element is composed of several naturally.

Comparing Atomic Mass and Mass Numbers Atomic Mass Mass Number The mass number is the total amount of protons and neutrons in an atom. An atom of an element.

This is the solution for carbon: (12) (0.9890) + (13) (0.0110) = amu mass number percent abundance % % Recall!!! carbon:

Average Atomic Mass!!!. Copper is made of two isotopes. Copper- 63 is 69.17% abundant and it has a mass of amu. Copper-65 is 30.83% abundant and.

Unit 3 Atomic Structure and Periodicity. Dalton’s Atomic Theory 1.All matter is composed of _____________. 2. Atoms of the same element are _______________.

Atomic Mass Mrs. Cook. Atomic Mass - The average relative mass of all naturally occurring isotopes of an element. relative mass – The mass of one object.

Isotopes are atoms of the same element that have a different number of neutrons For example, Hydrogen has 3 isotopes: Protium (0 neutrons) Deuterium (1.

4.5 Isotopes and Atomic Mass

Aim: How to Calculate the Average Atomic Mass?

ATOMIC STRUCTURE THE NUCLEUS: 1) THE PROTON:

Calculating Atomic Mass

Calculating Average Atomic Mass

Average atomic Mass.

Estimating the Mass Number:

Average Atomic Mass.

Atomic Structure.

Isotopes and Average Atomic Mass

Unit 2: Atomic Theory & Structure

Atomic Structure.

Mass of Individual Atoms

Section 2.4 Atomic Weights.

Calculating Average Atomic Mass

Average Atomic Mass.

Aim: How to Calculate the Average Atomic Mass?

Presentation transcript:

Calculating the Average Atomic Mass Number Where did that decimal come from?

Calculating Average Atomic Mass I CAN calculate the Average Atomic Mass Number of an element from its isotope data.

The Case for a Decimal We learned earlier that ATOMIC MASS NUMBER is the COMBINED NUMBER of P + and N o in an atom. Yet, the AMN given on the Periodic Table generally has a DECIMAL in it.

We discussed earlier that the AMN on the PT represents a WEIGHTED AVERAGE of all the ISOTOPES (atoms from the same element with varying numbers of N o ) of an element. Most elements have 2 OR MORE isotopes. Each different isotope always occurs in the SAME RELATIVE AMOUNT regardless of where the sample of the element is taken from.

For example: Lead has 4 isotopes: 1.40 % of all lead atoms are Pb % of all lead atoms are Pb % of all lead atoms are Pb % of all lead atoms are Pb-208 The UNIT for Atomic Mass is the ATOMIC MASS UNIT, abbreviated “amu” or simply “u”. How would you determine the AVERAGE ATOMIC MASS NUMBER of lead?

First of all, why can’t we simply add all the AMNs of the four isotopes up and find the average by dividing by 4? – We can’t do this because there is NOT AN EQUAL PERCENTAGE of each isotope. It they were all 25% each we could. Since there is not an equal percentage of each, they do not contribute equally to the overall average. Since we can’t do a simple average, we will have to calculate a WEIGHTED AVERAGE.

Calculating a Weighted Average To find a weighted average, EACH VALUE is MULTIPLED by its PERCENTAGE and the results are ADDED together. For Average Atomic Mass, the equation looks like this: Average AMN = Σ (Atomic Mass x Percentage) Σ = sigma = “find the sum of”

Practice Problem Lead has 4 isotopes: 1.40 % of all lead atoms are Pb -204, 24.10% of all lead atoms are Pb-206, 22.10% of all lead atoms are Pb-207, and 52.40% of all lead atoms are Pb-208. What is the average AMN for lead? STEPS 1. Multiple EACH mass by its percentage, making sure to move the decimal in the percentage TWO PLACES to the LEFT before multiplying. 2. Add the results and ROUND to SF.

Pb ux0.0140= u Pb ux0.2410= u Pb ux = u Pb u x0.5240= u _________ ≈ u

MORE PRACTICE Uranium has three common isotopes. If the abundance of U-234 is 0.01%, the abundance of U-235 is 0.71%, and the abundance of U-238 is 99.28%, what is the average atomic mass of uranium?

U-234 U-234 u x = u U-235 U-235 u x = u U-238 U-238 u x = u u (There are only 3 SF in ) ≈ u