Lesson 1 - Atomic Structure & Isotopes Flashcards
John Dalton’s Billiard Ball Model
-Matter is made up of tiny particles
-all atoms of element have identical properties
-atoms of diff elemts have diff properties
-atoms of 2 or more elements can combine in constant ratios to form new substances
-in chemical reactions atoms are not destroyed they simply join together
Review: Rutherford’s Gold Foil Experiment what they ASSUMED
-Positively charged beams go through gold foil and they should go right through
J.J. Thomson’s Plum Pudding Model
Atoms contain negatively charged electrons
Electrons are evenly distributed through the atom
Atoms are neutral, so there must be positive charges to balance out the negative charges
Review: Rutherford’s Gold Foil Experiment what they OBSERVATION
- Showed larger deflections and different directions
Review: Rutherford’s Gold Foil Experiment what they CONCLUSION
All of the atom’s positive charge and most of the atom’s mass were concentrated at a tiny point in the centre (the nucleus)
The electrons surrounded the nucleus and occupied most of the atom’s volume, but they only made up a small fraction of the atom’s total mass.
Chadwick’s Neutrons
discovered that the nucleus contains neutral particles (neutrons) as well as positively charged particles (protons)
Each neutron in an atom has about the same mass as…
each proton in the same atom, but the neutron carries no electrical charge
What makes up most of thre mass of the atom
Protons and neutrons
What did Bohr suggest about electrons
that electrons surround the nucleus in specific energy levels, each of which can hold a specific number of electrons
What makes the atoms of one element different from the atoms of another element?
The number of protons in the nucleus!
mass number =
= number of protons + number of neutrons
Isotopes
When you have 2 diff versions of an element it is called an isotope.
electrons
In a neutral atom, the number of electrons is equal to the number of protons
neutrons
The number of neutrons in an atom of an element depends on the mass number of the nucleus
Atomic mass
The difference of proportion of diff versions of elements, aka isotopes
What can atomic mass help us figure out?
Idenitfy most common isotpes
When an atomic mass is not a whole # what does it mean?
it as a weighted average of the masses of all the isotopes
Average Atomic Mass (AAM)
equation
- (AAM of isotope A x % of A) + (Atomic Mass of Isotope B x Mass of % B) +……
Calculate problem respectively
% must be a decimal
mass spectrometer
identify isotopes and their respective abundances
How does mass spectrometer work?
The sample is vaporized (converted to the gas phase by heating)
An electron beam bombards the vapors, which converts the vapors to ions
Because mass spectroscopy measures the mass of charged particles, only ions will be detected, and neutral molecules will not be seen.
radioactive decay
The disintegration of unstable isotopes
-The emitted nuclear radiation can take the form of energy or very small particles
The most common types of nuclear radiation are:
-alpha
-beta
-gamma
Alpha
positively charged particles with the same structure as the nucleus of a helium atom
-stopped by paper
Beta (β) particles:
negatively charged particles identical to electrons
-stopped by aluminum
Gamma (γ) rays:
a form of high energy electromagnetic radiation
-stopped by lead
Radioisotopes
Isotopes that decay to produce nuclear radiation
-For example, ALL of the isotopes of uranium are radioactive
Useful Radioisotopes
-iodine
-americium
-cobalt
-carbon
As you go up the perodic table the # of shells
decrease
As you go down the perodic table the # of shells
increase
All elements in a row (period) have the same….
number of energy levels
All elements in a column (group) have the same number of….
valence electrons
