Unit 4: Atoms and Compunds Flashcards
2 goals of alchemy
transmutation and panacea
describe 4 ways alchemy differs from chemistry
- alchemy methods are random and it uses philosophical principles ad system to describe, explain and predict the future while chemistry is systematic and it uses the scientific process to find patterns, describe, explain and predict the future
- findings in alchemy are kept secret and passed on only to apprentices while findings in chemistry are published and peer reviewed
- alchemist believed that matter was infinitely divisible, that things can become more than the sum of their parts and they believed in magic while chemists believe matter to be discrete, don’t believe in magic, but believe in atoms and believe that things are the sum of their parts
- alchemy’s scope is holistic as it integrates the material, psychological and spiritual while chemistry’s scope is specific as it is focused on the material
what are the 4 key points of Dalton’s atomic model?
- all substances are made of tiny solid, neutral, indivisible particles called atoms
- the atom of a given eleent are identical; the atoms of different elements are different in some fundamental way or ways
- chemical compounds are formed when atoms of different elements combine with each other and a given compound always has the same relative numbers and types of atoms
- chemical reactions involve reorganization of the atoms where the atoms themselves are not changed in a chemical reaction
describe Earnest Rutherford’s gold foil experiment and the significance of his results
Rutherford fired alpha particles at a thin sheet of gold foil, surrounded by detection shield. Based on Thomson’s model, the particles should’ve passed straight through but every so often, the particles would be deflected to another part of the screen. He realized that this could only happen if the radiation particles hit something super dense and solid which led him to discovering the nucleus and presenting a nuclear model in which all the mass of an atom was concentrated in a tiny nucleus in the center of the atom and he argued that atoms are primarily empty space.
what is an isotope and why are they important? give an example
isotopes are atoms of the same element that have the same number of protons, but a different number of neutrons. some isotopes are radioactive meaning that the nucleus is unstable and will eventually break down, releasing energy. radioactivity can cause radiation that can cause cancer, tissue decay and organism death
hydrogen-1 = hydrogen
hydrogen-2 = deuterium
hydrogen-3 = tritium –> radioactive
read how a mass spectrometer works
describe the events that lead to the creation of the new atomic theory, the Thomson model
when a high voltage is exerted to either end of a vacuum tube, tiny negative particles are able to be extracted from the atoms at one end. this showed that the atom is dividable. atoms are made by sub-atomic particles. Thomson proposed a model of the atom that had tiny negative particles embedded into the solid positive atom
how did Neil Bohr’s model differ from Rutherford’s?
Rutherford’s model dealt with the nucleus. Rutherford believed the electrons orbited around the nucleus in random patterns. Bohr’s atom model incorporates the nuclear nature of the atom but explains how the electrons are organized around the nucleus. Bohr states that there are specific increments of energy, each with a specific limit on the number of electrons that can exist at that energy level. The Bohr model can explain the spectral lines of hydrogen, and provides a guide as to how the spectral lines of other atoms can be understood.
name the three sub atomic particles and state their relative mass and charge
protons - 1.0 amu in the nucleus & +1 charge
neutrons - 1.0 amu in the nucleus & 0 charge
electrons - 0.0 amu at a great distance from the nucleus & -1 charge
describe the three types of changes that can occur when the number of a type of sub-atomic particle within the atoms of an element change
change in number of electrons —> you get ions
change in number of protons —> you get a new element
change in number of neutrons —> you get isotopes of the same element
how is the average atomic mass determined?
the average atomic mass is found by using a weighted average calculation where the various isotopes masses of the elements are multiplied by their respective percent abundance, then added to the next isotope multiplied by its percent abundance using the formula:
avg atomic mass = isotope1 (%1) +…+ isotopen (%n)
compare and contrast eight different properties of ionic and covalent bonds
- ionic bonds involve a give and take of electrons while covalent bonds involve a sharing of electrons
- ionic bonds are formed when metal and non-metal atoms interact forming cations and anions while covalent bonds are formed when non-metals and non-metals interact
- in ionic bonds, atoms become ions that form crystalline lattices when solid and in covalent bonds, atoms form molecules that stay together regardless of phase
- ionic bonds have high melting and boiling points while covalent bonds have low melting and boiling pints
- ionic bonds are able to conduct electricity while covalent bonds are generally insulators that cannot
- ionic bonds can dissociate into ions when dissolved called electrolytes, but only some covalent bonds can dissolve in water but they do not form electrolytes
- ionic compounds dissociate into cations and anions when they dissolve but covalent compounds do not dissociate and they remain whole molecules when they dissolve into solutions
- a metal, non metal pair have a very limited number of potential compounds that can be produced but a non metal, non metal pair may have a very large number of compounds that can be produced
what is a hydrate?
a hydrate is an ionic compound in solid crystalline form, that has water incorporated into its lattice
who is the person that proposed the idea of atomos?
Democratus
name the 3 philosophers in order of teacher then student
Socrates, Plato, Aristotle
