Flashcards in Chemistry: Chapter 4 and 5 [DONE] Deck (48):
What did Democritus reason about atoms?
he said that they were indivisible and indestructible; he turned Dalton's ideas into a scientific theory by using scientific methods
What do scientists use to observe atoms?
Scanning electron microscopes
define atom (2)
- the SMALLEST particle of an element
- it retains its identity in a chemical reaction
define Dalton's Atomic Theory: (4)
1. All elements are composed of atoms
2. atoms of the same element are identical, but atoms from different elements are ALL different
3. atoms of different elements can mix together to form a compound
4. chemical reactions occur when atoms are separated from each other, joined, or rearranged in a different combination. *Atoms of one element can NEVER be changed into another element from a chemical reaction.
What are the three types of subatomic particles?
What are their charges?
What are their masses?
- protons, neutrons, and electrons
- positive, neutral, and negative
- 1, 1, 1/1840
What is the actual structure of a nuclear atom?
- Protons and neutrons are contained inside of the nucleus.
- Electrons reside in orbitals AROUND the nucleus
who discovered electrons?
- a negatively charged subatomic particle
- J.J. Thomson
define cathode ray:
what was the final results in the experiment conducted by J.J. Thomson
- a glowing beam that Thomson used in an experiment
- found that a positively charged plate ATTRACTS the cathode ray and a negatively charged plate REPELS the cathode ray.
who discovered protons?
- a positively charged subatomic particle
- Ernest Rutherford
who discovered neutrons?
- a neutrally charged subatomic particle
- James Chadwick
- the center / core of an atom
What was later discovered about atoms?
- that they actually ARE divisible, which means that they can be divided without losing their properties.
what makes one element different from another?
the number of protons
*every element has a different number
How do isotopes of an element differ?
because isotopes of an element have a different number of neutrons and different mass numbers
How to calculate the atomic mass of an element?
(mass of isotope x natural abundance in decimal form = x ) + (mass of isotope x natural abundance in decimal form = x), etc...
* do that for however many isotopes it gives you and then add the products
define atomic number
the number of protons in the nucleus of an atom of the element
define mass number
total number of protons and neutrons in an atom
What did Niels Bohr propose in his model of the atom?
He proposed that an electron is found only in orbits around the nucleus.
what does the quantum mechanical model determine about the electrons in an atom?
the allowed energies an electron can have and how likely It is to find the electron in various locations?
How to find the number of neutrons in an atom?
# of neutrons = mass # - atomic #
* Mass # = rounded to a whole number
atoms of the same element that have the same atomic number, but different atomic masses due to a different number of neutrons
How to find protons?
it's the atomic number of an element
define quantum mechanical model
the behavior of electrons in atoms
how to find electrons
*same as the number of protons
define atomic orbital (2)
a mathematical expression describing the probability of finding an electron at various locations
represented by the denser area surrounding a nucleus (higher probability of finding an electron)
define atomic mass
the weighted average of the masses of the isotopes of an element
define atomic mass unit (amu)
a unit of mass equal to one-twelfth the mass of a carbon-12 atom
What were the ideas concerning the structure of an atom involving Thomson and Rutherford?
Thomson - believed that electrons were evenly distributed throughout the atom filled uniformly with positively charged material.
Rutherford - tested Thomson's model of atomic structure through the gold-foil experiment --> led to his idea that the atom was mostly empty space
define energy level
the specific energies an electron in an atom or other system can have
what causes atomic emission spectra? (2)
- absorbing energy (electrons move to higher energy levels)
- emitting light (loses electrons when they return to lower energy levels)
How does quantum mechanics differ from classical mechanics?
- classical mechanics describe the motions of bodies much larger than atoms
- quantum mechanics describes the motions of subatomic particles and atoms as waves
the amount of energy needed to move an electron from one energy level to another
what is the unit for wavelength?
- the distance between adjacent crests of a wave
- measured in meters
what is the unit of frequency?
- the # of wave cycles that pass a given point per unit of time
- Hertz (Hz) or s^-1
define electromagnetic radiation
energy waves that travel in a vacuum at a speed of 2.998 x 10^8 m/s
(c= wavelength x frequency)
what are the 3 rules for writing the electron configuration of elements?
* what does it do?
1. the Aufbau Principal
2. the Pauli Exclusion Principle
3. Hund's Rule
* it tells you how to find the electron configurations of atoms
how did Einstein explain the photoelectric effect?
he proposed that light could be described as quanta of energy that behave as if they were particles
define atomic emission spectrum
the pattern formed when light passes through a prism
define Planck's Constant
(h) a number used to calculate the radiant energy (E) absorbed or emitted by a body based on the frequency of radiation
E = (6.626 x 10^-34) x frequency
define electron configuration
the arrangement of electrons of an atom in its ground state into various orbitals around the nuclei of atoms
a quantum mechanical property of electrons that may be thought of as clockwise or counterclockwise
the height of a wave's crest
what is the order of the electromagnetic spectrum from lowest frequency to the highest frequency:
what are the colors?
Radio Waves, Radar, Microwaves, Infrared, Ultraviolet, X-Rays, Gamma Rays
order of the electromagnetic spectrum from lowest wavelength to the longest wavelength:
Gamma Rays, X-Rays, Ultraviolet, Infrared, Microwaves, Radar, Radio Waves
define photoelectric effect:
the ejection of electrons by certain metals when they absorb light with a frequency above a threshold frequency
a quantum (amount of energy needed to move an electron from one level to another) of light
- a discrete bundle of electromagnetic energy that interacts with matter similarly to particles
define ground state
the lowest possible energy of an atom described by quantum mechanics