Unit 2 - Atomic Structure Flashcards
(23 cards)
Democritus discovered
Studied under Greek Philosopher Leucippus.
matter was composed into tiny particle called “a tomos”
“a tomos:” uncuttable or indivisible
JJ Thomson discovered
Estimated mass of rays of cathodes weren’t rays but slightly charged particls or as we call them: electrons
Made the Plum Pudding Method where the pudding is positive and the floating fruit is negative
John Dalton discovered
(challenged Aristotle)
Provided first empirial evidence that atoms exist by proposing that compounds consist of different types of atoms in whole # ratios and that chemical reactions involve rearrangements to give new combinations
Billard Ball Model
5 Postulates:
1. All matter is made of atoms
2. All atoms of same element are identical
3. Atoms cannot be created nor destroyed
4. Combine in whole # ratios by mass
5. Atoms can be separated, rearranged, or combined
Earnest Rutherford discovered
He experimented with a thin sheet gold foil & screen with zinc sulfide and then bombarded it with particles. Some went through but some deflected meaning that there must be a nucleus with a positive charge.
Most of the atom is empty space.
Neils Bohr discovered
electrons in orbits around a central nucleus with each orbit having a specific # of electrons which correlates to energy levels
Planetary Model
Quantum Theory
or cloud model or Quantum Mechanical Model
electrons weren’t particles or waves, instead they had properties of both and neither meaning that the arrangement of electrons around a nucleus could only be described in probability.
Orbitals
region where an electron is more likely to be found
Millikan discovered
charge of electron to be negative
Atomic Number (Z)
number of protons, also equals electrons if atom is neutral
Mass Number (A)
number of protons & neutrons
Neutrons
mass number - atomic number
mass-protons
Isotope
atoms with differing numbers of neutrons
Periodic table will show the average atomic mass
i.e.: k-39, k-40, k-41
Average Atomic Mass
mass based on the average of all isotopes of an atom
unites are AMU
solve by multipling isotope times abundance, then add each answer to equal average atomic mass
Column
up or down
group or family
18 of them
Row
side to side
period
7 of them
Metals
where are they and what are their properties
left side; heat conductors, malleable, shiny, ductile
Non-metals
where are they and what are their properties
right side, opposite metal properties
most are gases
Metalloids
found on the stair step line and has properties of both
most common is silicon
elements are grouped into ____ based on their ____ properties
families; chemical
elements
in the same group
have similar properties, same # of valence electrons, and same oxidation number
-Valence Electrons: electrons that are closer to the nucleus are in filled orbitals and are called core electrons. Valence electrons are the farthest from the positive charge (the protons) and thus tend to be easier to remove than core electrons; this means that it takes them less energy to move far away from the atom.
-Oxidation Number: hypothetical charge of an atom if all of its bonds to other atoms were fully ionic
reactivity
for metals and non-metals
metals-reactivity increases as you go down the table
non-metals-reactivity decreases as you go down the table
Dmitri Mendeleev
contributed ascending atomic mass
Henry Moseley
contributed ascending atomic number
