Chem Ch 2.txt

3 particles in an atom:

Protons, Electrons, Neutrons

Protons

mass=1amu; Positive Charge;atoms of diff elements have diff # protons

Electrons

Negative Charge; 1 for each proton in all neutral atoms

Neutrons

mass=1amu; no charge(create stability in nucleus); atoms of a given element can have a variable #

Isotopes

atoms of a given element (same # protons) with diff # of neutrons

Each Isotope has

a mass number; the sum number of protons and neutrons

Atomic mass

the blended average weight of an element with isotopes

Aragadros Number

6.02x10^23 = 1 mole

1 mole

equal to the atomic mass in g of any element

molecular weight of a compound

the sum of the atomic weights of all the elements in the compound

72 -1...Br 35

72=mass #-1=charge35=atomic number

How many neutrons with a mass of 72 and atomic number of 35?

37

How many electrons with a atomic number of 35 and charge of -1?

36