[http://www.csmate.colostate.edu/cltw/cohortpages/viney_off/atom.jpg]

ProtonsProtons

• Found in the nucleus.

• Equal the atomic number of an element.

• These always identify the element!

• + 1 Charge

• Atomic mass = 1 amu

[http://imagine.gsfc.nasa.gov/Images/try_this/helium.gif]

NeutronsNeutrons

• Found in the nucleus.

• Atomic mass minus Atomic number equals # of neutrons

• Atomic mass = 1 amu

• No charge (neutral)

[http://imagine.gsfc.nasa.gov/Images/try_this/helium.gif]

ElectronsElectrons

• Found in “clouds” around the nucleus

• Same number as the protons when the atom is neutral!

• -1 charge

• Atomic Mass = 0 amu

[http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/TB02_01.JPG]

Protons, Neutrons, & Protons, Neutrons, & ElectronsElectrons

• Example: How many protons, neutrons, and electrons does the element Sodium have?

• p+ = 11 (the atomic number)

• n = 12 (mass – atomic number)

• e- = 11 (neutral atoms have same numbers of protons and electrons)

Protons, Neutrons, & ElectronsProtons, Neutrons, & Electrons

• Example: What about Copper?

• p+ = 29

• Round the mass of 63.5 up to 64

• n = 35

• e- = 29

Protons, Neutrons, & ElectronsProtons, Neutrons, & Electrons

IsotopesIsotopes

• Some atoms have a different mass because they have more or less neutrons than normal.

• Can be written two ways…

Carbon - 14Carbon - 12

Isotopes of Hydrogen

Normal

[http://wps.prenhall.com/wps/media/objects/602/616516/Media_Assets/Chapter02/Text_Images/FG02_06-02UN.JPG]

IsotopesIsotopes

• Example: How many p+, n, e-, are there in Chlorine – 37?

• p+ = 17 (atomic number)

• n = 20 (new mass – protons!)

• e- = 17 (neutral atom)

IsotopesIsotopes• The atomic masses on the periodic table

are averages of all the known isotopes of certain elements.

75.5% 24.5%

75.5% 24.5%

35 x 0.755 = 26.4337 x 0.245 = 9.07+

Periodic Table Mass = 35.5