Phy Sci chapter four Flashcards
What did Democritus suggest
He suggested that the universe was made of invisible units called atoms
Who came up with the first theory of atoms
Democritus
What did Dalton add to the atomic theory
That all atoms of a given element were exactly alike and atoms of different elements could join to form compounds
A chemical compound always contains the same elements in exactly the same proportions by weight or mass
Law of definite proportions
How did Thompson discover the electron
Thomson’s cathode-ray tube experiment suggested that cathode rays were made of negatively charged particles that came from inside atoms
What model did Thomson develop
The plum pudding model
A subatomic a particle that has a negative charge
Electron
What is Rutherford’s atomic model
Rutherford proposed that most of the mass of he atom was concentrated at the atom’s center
What experiment did Rutherford conduct
The gold-foil experiment
What part of the atom did Rutherford discover
Nucleus
An atom’s central region, which is made up of protons and neutrons
Nucleus
What two particles are there an equal amount of in an atom
Protons and electrons
This is how positive protons are attracted to negative electrons
Electric force
What do atoms of an element have in common with other atoms of the same element
Atoms of each element have the same number of protons, but they can have different numbers of neutrons
The number of protons in the nucleus of an atom
Atomic number
The sum of the numbers of protons and a neutrons in the nucleus of an atom
Mass number
Why do isotopes of the same element have different atomic masses
Isotopes of an element vary in mass because their number of neutrons differ
Unstable isotopes that emit radiation and decay into other isotopes
Radioisotopes
What formula is used to calculate the number of neutrons
Number of neutrons = mass number - atomic number
What unit is used to express atomic mass
Unified atomic mass units
A unit of mass that describes the mass of an atom or molecule
Unified atomic mass unit
What is the mole used for
Counting small particles
The SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in exactly 12g of carbon-12
Mole
What is the abbreviation for mole
Mol
What is one mole equal to
602,213,670,000,000,000,000,000 partic
6.022 x 1023
What is the number for mole called
Avogadro’s number
The mass in grams of one mole of a substance
Molar mass
How do you find the amount of moles in an element
mass x 1 mol of element / molar mass of element
How do you find the mass of moles in an element
amount x molar mass of element / 1 mol of element
How do you find the molar mass go a compound
Add up the molar masses of all the atoms in a molecule of the compound
What is the modern model of the atom
Electrons can be found only in certain energy levels, not between levels
Who’s model states that electrons can be in only certain energy levels
Bohr’s
How do electrons move to a higher energy level
They gain energy
How do electrons move to a lower energy level
They lose energy
What do electrons act like
Waves
A region in an atom where there is a high probability of finding electrons
Orbital
How are the energy levels of an atom filled
The number of energy levels that are filled in an atom depends on the number of electrons
An electron yay is found in the outermost shell of an atom and that determines the atom’s chemical properties
Valence electrons
What are the 4 types of orbitals
s
p
d
f
How many electrons can each orbital hold
2
What determines the number of electrons that each level can hold
Orbitals
What makes an electron jump to a new energy level
When an atom gains or loses energy
The lowest state of energy of an electron
Ground state
An electron gains energy by absorbing a photon so it moves to an
Excited state
A unit or quantum of light
Photon
When does an electron release a photon
When it falls back to a lower level
What is a type of “atomic fingerprint” that can be used to identify the substance
The wavelengths emitted by the element
