1. Chapter 3 Sec 3 Counting Atoms
All atoms are composed of the same three particles, but not all atoms are the same.
Atomic number – of an element is the number of protons in the nucleus. The number of protons makes the element that specific element. As a NOTE elements have the same number of electrons as the number of protons.
Atomic mass – of an element is number of protons and neutrons combined in the nucleus.

3. Isotopes
Isotopes of elements have the same number of protons but a different number of neutrons in the nucleus.
Isotopes have different masses because of the additional neutrons but they don’t differ significantly is their chemical properties.
Nuclide is a general term for a specific isotope of an element

4. isotopes To find the number of neutrons any element has:
Atomic mass – atomic number = number of neutrons for that element
Hydrogen - 1 atomic mass – atomic number = # neutrons
= 0 neutrons
But hydrogen has 2 isotopes
Protium – has 1 p , 1 e and 0 n (hydrogen – 1 )
Deuterium – has 1 p , 1 e and 1 n (hydrogen – 2 )
Tritium – has 1 p , 1 e, and 2 n (hydrogen – 3 )

5. Elements nuclear symbol
The nuclear symbol is a way to write elements information
Hydrogen – 𝑎𝑡𝑜𝑚𝑖𝑐 𝑚𝑎𝑠𝑠 𝑎𝑡𝑜𝑚𝑖𝑐 𝑛𝑢𝑚𝑏𝑒𝑟 atomic symbol
1 1 H
Hydrogen – Carbon C Helium He
2 1 H

6. Hyphen notation
Element name – element’s atomic mass (rounded to whole number)
Hydrogen – 1
Hydrogen – 2
Helium – 3
Helium - 4

7. Atomic mass units Atomic mass units (amu)
Atomic mass unit ( amu) = the atomic mass of an element
Helium has an atomic mass of so helium has 4.0 amu
Magnesium has an atomic mass of so
magnesium has amu

8. Calculating Average atomic mass
Since elements and their isotopes are found in the same area, to calculate the average atomic mass we have to include the percent of the isotope and well as the percent of the element:
%natural atomic mass
occurance
Copper –
Copper –
69.15 x x = amu

9. The MOLE Mole is a term we use for the number 6.022 1314 x 1023
1 mole is 602 billion trillion
Abbreviated mol and x 1023
1 mole = 6.02 x 1023
Just like dozen is used for the number 12
We could have 1 mole of anything
Soda cans 1 mole would equal 602 billion trillion soda cans
Pop corn kernels 1 mole would equal 602 billion trillion popcorn kernels

10. The Mole
To give you a better idea of how many 6.02 x 1023 popcorn kernels would be:
602 billion trillion popcorn kernels would cover the United States to a depth of over 9 miles
602 billion trillion soda cans would cover the Earth to a depth
Depth of 200 miles

11. The Mole 6.02 x 1023 is often referred to as Avogadros numbers.
Amedeo Avogadro, discovered while working with gases that no matter what the gas was there was the same number of molecules present.