moles, atoms and elements

a mole of things weight

proportionally more than a mole of lighter things

so we can say For instance, argon has an atomic weight of 39.95 amu.  Neon has an atomic weight of 20.18 amu.  So, we can say:

-1 argon atom weighs twice as much as 1 neon atom.

-A dozen argon atoms weigh twice as much a dozen neon atoms.

-A thousand argon atoms weigh twice as much as a thousand neon atoms

-1 mole of argon atoms weighs twice as much a mole of neon atoms.

avogadros number

6.022 × 10²³

also the bumber of amus it takes to make one gram

a single copper atom has an average mass of 63.456 amu, so a mole of copper atoms has a mass of 63.546 g

atomic weight or atomic mass

this is the mass of a single individual atom in units of atoms

average atomic weight ( or average atomic mass)

this is the weighted average mass of a single atom in units of amu

average molar mass (often referred to as molar mass)

this is the mass in grams of one mole of an element or compound. it is in units of grams/mole

protons mass and charge

1.00727 amu

1.67262 × 10^-27 kg

1+ charge

neutron mass and charge

1.00866 amu

1.67493 × 10^-27 kg

0 charge

electron mass and charge

0.00055 amu

0.00091 × 10^-27 kg

1- charge

how many known elements or types of atoms that make up all matter in the universe as far as we know

118

isotopes

Although all atoms of the same element have the same number of protons, the number of neutrons in the nucleus may vary.  Atoms with the same number of protons but different number of neutrons are called

same atomic number but different mass number

atoms

electrically neutral meaning they have the same number of electrons as protons

ions

are atoms with a net charge arising from an imbalance of protons and electrons resulting from a loss or gain in electrons.  An atom cannot lose or gain protons

positive ions

cations

negative ions

anions

how do we actually determine the fractional natural abundance of isotopes

We use a technique known as Mass Spectroscopy or “Mass Spec.”

1.Elemental sample is heated to vaporization

2.Electron beam ionizes the atoms by removing electrons.  Since they are all the same element you get the same ion.

3.Electrically charged plates set up E field that accelerates the ions into a beam (called ion beam).

4.Ion beam goes through a magnetic field which separates the ions by deflection based on mass to charge ratio.  Since charge is constant, the lighter isotope’s ions are deflected more than the heavier ones.