Day 2 Notes Atomic Number, Mass Number, Concluding Neutrons

For neutral elements (no charge) the

(#) number of protons (=) equals (#) number of electrons

Isotopes

-Atoms with the same number of protons, but different number of neutrons -They are chemically alike -Have different mass numbers Written like this: element- mass number

Mass Number

-Number of protons and neutrons combined -It is always a whole number

Atomic Mass

-Read right off the periodic table -The number will have a decimal It is the WEIGHTED AVERAGE of all elements isotopes

Atomic Number

-The number of protons in an element -It is always a whole number Ex: Oxygen's ___ is 8, therefore there are 8 Protons in Oxygen's nucleus

To find the number of Neutrons

= mass (#) - atomic (#) Ex: Oxygen's mass number is 16 and its atomic number is 8. The number of ____ will be 8

Summary

Atomic # = protons = elements ( for neutral atoms) Mass # = protons + neutrons Neutrons= mass # - atomic #

It is like our

social security number, it identifies them

The number of protons

will never change for an element