Bell WorkCompare and contrast the Bohr model and the Quantum Mechanical Model.

http://www.youtube.com/watch?v=vUzTQWn-wfE&list=PL701F0464C7551022

Sticky Note Matching Game

• Each one of you has been given an index card with a name, facts, or diagram. Now you have to find the name, facts and diagrams that match (not every name has a diagram).

• The Catch: you can only use ‘yes’ or ‘no’ questions to try to find the matches.

• When you find all the matches, read over the cards and prepare a 1-3 minute explanation.

The Subatomic Particles and the Structure of the Atom

Distinguishing Among Atoms

• Structure

• Atomic/ Mass Number

• Isotopes

• Atomic mass

•The atomic number is the number of protons in an atom.

•This number is unique for all elements and is used to identify each element.

•Atoms are electrically neutral therefore:

# PROTONS = # ELECTRONS.

Mass Number is the total number of protons and neutrons in an atom

Mass number = # protons + # neutrons

Atomic number = # protons = # electrons

Mass number – Atomic number = # neutrons

Average

10 protons10 neutrons10 electrons

10 protons11 neutrons10 electrons

10 protons12 neutrons10 electrons

• Isotopes are atoms of the same element that differ in the number of neutrons.

Isotopes of the same element have the same chemical properties, because they have the same number of protons and electrons.

Isotopes are identified by mass number. Neutrons affect mass, so, isotopes with more neutrons are heavier

Sample Problem

Three isotopes of oxygen are oxygen-16, oxygen-17, and oxygen-18. Write the symbol for each, including the atomic number and mass number.

http://www.youtube.com/watch?v=EboWeWmh5Pg

Atomic Mass

• The actual masses of individual atoms are very very very very small (arsenic = 1.244 x 10 -23 )…so to measure the relative mass of atoms, a reference isotope is used.

• The reference isotope is carbon-12. It has a mass of exactly 12 atomic mass units.

• Atomic mass units (amu) is the unit used.

Atomic Masses

Isotope Symbol Composition of the nucleus

% in nature

Carbon-12 12C 6 protons 6 neutrons

98.89%

Carbon-13 13C 6 protons 7 neutrons

1.11%

Carbon-14 14C 6 protons 8 neutrons

<0.01%

Atomic mass is the weighted average of all the naturally occurring isotopes of that element.

Carbon = 12.011amu

To calculate relative atomic mass, multiply the mass number of each isotope by its percent abundance changed to a decimal and total.

(Mass #)(isotope’s relative abundance) +

(Mass #)(another isotopes Rel. abundance) =

Relative atomic mass of the element

Example 1: Neon has 2 isotopes, Ne-20 with an abundance of 90% and Ne-22 with an abundance of 10%. Calculate the average atomic mass of neon.

20 x 0.9= 18

22 x 0.1= 2.2

18 + 2.2 =20.2 amu

Why is it closer to 20 than 22?

20 is more abundant

Example 2: Carbon occurs in nature as a mixture of atoms of which 98.89% have a mass of 12.00 u and 1.11% have a mass of 13.00335 u. Calculate the atomic mass of carbon. 12.00 x 0.9889= 11.87

13.00335 x 0.0111= 0.144

11.87+ 0.144 = 12.014

Why is it closer to 12?

12.00 is more abundant

Sample Problem

Carbon has two stable isotopes: carbon-12 which has a natural abundance of 98.89 % and carbon-13 which has a natural abundance of 1.11 %. The mass of carbon-12 is 12.000 amu and the mass of carbon-13 is 13.003 amu. What is the atomic mass?

Sample Problem

The element antimony (Sb) has naturally occurring isotopes with mass numbers of 121 and 123. The relative abundance and atomic masses are 57.12 % for mass = 120.90 amu, and 47.29% for mass = 122.90 amu. Calculate the atomic mass of antimony.

Sample Problems

In book, page 119 numbers 24 and 25

Meet 115, the newest element on the Periodic Table, Ununpentium

• Man-made element first by Russian scientist 10 years ago. It was replicated by chemists in Sweden at the Lund University. Therefore making it officially a new element.

• No official name has been given yet, so scientists are calling it Ununpentium, based on the Latin and Greek words for its atomic number 115.

• http://www.rsc.org/periodic-table/element/115/ununpentium