Structure of the Atom – Atomic Facts
Ch 03 notes
Structure of the atomThe atom has TWO main parts:
1. Nucleus
2. Electron CloudAtoms are electrically neutral
A. Overall charge of an atom is ZEROB. electrons = protons
The Nucleus• Central portion of atom • Make up most of the mass of the atom• Contains two subatomic particles• protons – positive charge(+)
• makes the atom unique
• 1.67266 x 10-27 kg
• neutrons –neutral, no charge(0) • this number can change—still have same element
“isotope”
•1.67495 x 10-27 kg
Electron Cloud
• surrounds the nucleus • electrons –negative • mass of the electron is = 9.11 x 10 -
31 kg• Sub-atomic particle involved in
bonding
Atomic Factsatomic number • the number of PROTONS in the
nucleus
Average atomic mass• the average mass of an atom
of this element, expressed in atomic mass units.
oBecause atoms are so small we use an atomic mass unit(u) = to find the mass of one atom
1 amu = 1.66 X 10-
24 g
6 12.0107
C Carbon
Isotopes• Atoms of the same element with a different number of
neutrons.• http://education-portal.com/academy/lesson/isotopes-and-
calculation-of-a-weighted-average.html
Average atomic mass is a weighted average of these isotopes
• Isotopes have a different mass number but identical atomic number
• The MOST COMMON isotope is represented on the PTE!!!
• https://www.youtube.com/watch?v=pV822HfqT44
Writing Isotopes
Br8135
Bromine-79
Bromine-81
http://www.webelements.com/isotopes.html
More EX: Oxygen, Boron,
Atomic Factso Mass number – number of
protons + neutrons in the nucleus---whole number
o IF NOT GIVEN: Round avg. atomic mass to nearest whole number.
Mass number – atomic number =
neutrons• The number of protons = the
number of electrons– atoms are electrically neutral
8 15.999
O Oxygen
Oxygen-16
Cl
35.45317
Chlorine
Isotopes of Chlorine: Chlorine-35 and Clorine-37Isotopes of Bromine: Bromine-79 and Bromine-81
http://education-portal.com/academy/lesson/isotopes-and-calculation-of-a-weighted-average.html
35 79.904
BrBromine
https://www.youtube.com/watch?v=pV822HfqT44
Calculating Average Atomic Mass
What you need: Percent (%) abundance of each isotope in decimal form
Mass( in amu’s) of each isotope of the element
How to calculate the weighted average by:
1.(mass isotope 1) • (percent abundance in decimal form)=
2.(mass isotope 2) •( percent abundance in decimal form)=
3.(mass isotope 3)• ( percent abundance in decimal form)=
ADD ALL TOGETHER!!!
Calculate the Average Atomic Mass
Mass of Isotope Abundance
24.0 amu 78.70%
25.0 amu 10.13%
26.0 amu 11.17%
Calculate the average atomic mass. What element is this?
Calculate the Average Atomic Mass
• A certain element is a soft, silvery-white metal that has two common isotopes, the first isotope has a mass of 85.0 amu’s the second isotope has a mass of 87.0 amu’s .
• If the abundance the first isotope is 72.2% and the abundance of the second isotope is 27.8%, what is the average atomic mass of this element? What is the element?
Atomic FactsChemical symbols – the abbreviated way to write the
name of an element– a capital letter– cap letter AND lower case letter. – Others come from their Latin name ( Argentum
Ag : silver)
Co vs. COMetal that forms bright
blue solid compounds.
Poisonous gas
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