Wake-up 1.Explain the relationship between the following: atomic number, mass number, protons, neutrons, and electrons. 2.How do you find the number of.

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Wake-up 1.Explain the relationship between the following: atomic number, mass number, protons, neutrons, and electrons. 2.How do you find the number of electrons of an element? 3.How do you find the number of neutrons of an element?

Isotopes and Relative Abundance What is an isotope? What is relative abundance?

Examine the information of hydrogen below and answer the following questions. Do not round the mass number!

What element and chemical symbol is shown? Hydrogen and H

What is the atomic number for this element? 1

What is the atomic mass for this element? Don’t round 1.00794

List the number of protons, electrons, and neutrons (in that order) 1 p +, 1 e -, 0 n 0

What is an ISOTOPE? Isotope = atoms that have the same number of PROTONS but different number of NEUTRONS. Chemically alike but with varying mass numbers

APPLE VARITIES

In other words, all the isotopes of the same element (atom) have the SAME but DIFFERENT Atomic Number (p + and e - ) Mass Number (specifically n 0 )

Review Notations Hyphen notation: Write the element name and the mass number Hydrogen - 1 Mass Number

Review Notations Nuclear notation: See diagram below

Examine the mass number of the various elements on the periodic table. Very few are even. This is due to isotopes. The mass number is better known as the Atomic Mass or Atomic Unit. This number represents the AVERAGE mass of all the naturally occurring isotopes of an element.

Atomic Mass Average of the masses of an elements (atom) naturally occurring isotopes

Relative Abundance The abundance isotopes of an element as naturally found on a planet (%) Relative abundance of elements on Earth’s surface

Isotope: Hydrogen-1 Name: Protium (Most common isotope of Hydrogen has a 99.985% relative abundance)

Isotope: Hydrogen-1 # of Protons: 1 # of Electrons: 1 # of Neutrons: 0

Isotope: Hydrogen-2 Name: Deuterium (Relative Abundance: 0.015% of Hydrogen)

Isotope: Hydrogen-2 # of Protons: 1 # of Electrons: 1 # of Neutrons: 1

Isotope: Hydrogen-3 Name: Tritium (Relative Abundance: Very small amounts of Hydrogen)

Isotope: Hydrogen-3 # of Protons: 1 # of Electrons: 1 # of Neutrons: 2

Calculating Average Atomic Mass Formula: ( % abundance #1)(Mass #1) + (% abundance #2)(Mass #2) 100

Calculating Average Atomic Mass #1 You have a box containing two sizes of marbles. 25% of the marbles have a mass of 2.0 g. 75% of the marbles have a mass of 3.0 g. Calculate the average weight of the marble.

Example #2: Rubidium has two common isotopes, 85 Rb and 87 Rb. If the abundance of 85 Rb is 72.2% and the abundance of 87 Rb is 27.8%, what is the average atomic mass of rubidium?

Example #3: The element boron has two stable isotopes. Boron- 10 has an atomic mass of 10.0129 and a percentage in nature of 19.78% The atomic mass of boron-11 is 11.0093 and its percentage in nature is 80.22% What is the average atomic mass for boron?

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