Chemistry Chapter 4 and 5 test – Flashcards
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atom
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smallest particles of an element that retains its identity in a chemical reaction
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how did Democritus describe atoms?
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he believed that atoms were indivisible and indestructible; cannot be divided
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how did John Dalton further Democritus's ideas on atoms?
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by using experimental methods dalton transformed democritus's ideas on atoms into scientific theory; he created the modern theories about atoms
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what instruments are used to observe atoms?
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even thought individual atoms are small in six, they are observable with instruments such as scanning tunneling microscopes
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dalton's atomic theory
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first theory to relate chemical changes or events at the atomic level 1) all elements are composed of tiny indivisible particles (atoms) 2) atoms of the same element are identical 3) atoms of different elements can physically mix together/ can chemically combine in simple whole number ratios to form compounds 4) chemical reactions occur when atoms are separated, joined, or rearranged
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what are three kinds of subatomic particles?
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electrons, protons and neutrons
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how can you describe the structure of a nuclear atom?
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protons and neutrons are located in the nucleus, the electrons are distributed around the nucleus and occupy almost al the volume of the atom
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electrons
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negatively charges subatomic particles
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cathode ray
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a glowing beam traveling between charged electrodes
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protons
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positively charged subatomic particles
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neutrons
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subatomic particles with no charge
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nucleus
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tiny central core of the an atom composed of protons and neutrons
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anode
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an electrode with a positive charge
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cathode
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an electrode with a negative charge
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how many atoms of copper when placed side by side would form a line 1 cm long?
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100,000,000
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how does the atomic theory differ from dalton's atomic theory?
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atoms are known to be divisble, they can be broken down into subatomic particles: electrons, neutrons and protons
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what 2 properties of an electron did Robert Millikan determine from his experiments?
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an electron carries one unit of negative charge and its mass is 1/1840
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thomson discovered the electron using a cathode ray. what did thomson reason from his experiment?
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electrons are part of the atoms of all elements and electrons and negatively charged
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electric charges
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carried by particles of matter, always exist in whole-number multiples of a single basic unit
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when a number of protons combines with an equal number of electrons what charge is formed?
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neutral
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what charge does a neutron carry?
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no charge
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positively charge subatomic particle that stays when a hydrogen atom loses an electron is a ______
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proton
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alpha particle
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has a double positive charge because it is a helium atom that has lost two electrons
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what did the rutherford experiment show?
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an atom is mostly empty space, all positive charge of an atom is concentrated in the nucleus and nearly all the mass of an atom is in its nucleus
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atomic number
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number of protons in the nucleus of that element
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what makes one element different from another?
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they contain different numbers of protons
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mass number
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total number of protons and neutrons in an atom
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how do you find the number of neutrons in an atom?
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difference between mass number and atomic number
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how do isotopes of an element differ?
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because they have different numbers of neutrons, they also have different mass numbers
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how do you calculate atomic mass of an element?
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multiply the mass of each isotope by its natural abundance, expressed as a decimal and then add the products
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why is the periodic table useful
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allows you to easily compare the properties of an element to another element
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isotopes
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atoms that have the same number of protons but different numbers of neutrons
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what are 3 isotopes of hydrogen
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hydrogen-1; hydrogen-2; hydrogen-3
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atomic mass unit (amu)
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unit of mass equal to one twelfth the mass of a carbon-12 atom
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atomic mass
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weighted average mass of the atoms in a naturally occurring sample of an element
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periodic table
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arrangement of elements where the elements are separated into groups based on a set of repeating properties
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group
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each vertical column in the periodic table
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period
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each horizontal row of the periodic table
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what was inadequate about rutherford's atomic model?
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it could not explain the chemical properties of elements
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what was the new proposal in the bohr model of the atom?
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proposed that an electron is only found in specific circular paths, or orbits around the nucleus
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what does quantum mechanics determine about the electrons in an atom?
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determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus
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how do sublevels of principal energy levels differ?
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each energy level corresponds to an orbital of a different shape, which describes where the electron is likely to be found
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energy levels
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fixed energies an electron can have
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quantum
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amount of energy required to move an electron from one energy level to another
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quantum mechanical model
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modern description, primarily mathematical; of the behavior of electrons in atoms
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atomic orbital
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region of space in which there is a high probability of finding an electron
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electron configurations
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way in which electrons are arranged in various orbitals around the nuclei of atoms
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Aufbau principle
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says electrons occupy the orbitals of the lowest energy first
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pauli exclusion principle
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says atomic orbitals may describe at most 2 electrons
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hund's rule
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states that electrons occupy orbitals with the same energy in a way that makes the number of electrons with the same spin direction as large as possible
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what are 3 rules for writing electron configurations of elements?
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aufbau principle, pauli exclusion principle, and hund's rule
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why do actual electron configuration for some elements differ from those assigned using the aufbau principle?
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they differ from those assigned using the aufbau principle because half-filled sub levels are not stable as filled sublevel but they are more stable than other configurations
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amplitude
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wave's height from zero to the crest
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wavelength
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distance between crests
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frequency
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number of wave cycles to pass a given point per unit of time
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hertz
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SI unit of cycles per second
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electromagnetic radiation
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radio waves, microwaves, infrared wave, visible light, ultraviolet waves, x-rays and gamma rays
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spectrum
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wavelengths of visible light that are separated when a beam of light passes through a prism; range of wavelengths of electromagnetic radiation
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atomic emission spectrum
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pattern formed when light passes through a prism or diffraction grating to separate it into the different frequencies of light it contains
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ground state
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lowest possible energy of the electron
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photons
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light quanta
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heisenberg uncertainty principle
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states that it is impossible to know exactly both the velocity and position of a particle at the same time
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how are the wavelength and frequency of light related?
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they are inversely proportional to each other
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what causes atomic spectrum
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when atoms absorb energy, electrons move into higher energy levels and these electrons lose energy by emitting light when they return to lower energy levels
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how are frequencies of light an atom emits related to the changes of electrons energies
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the light emitted by an electron moving from a higher to a lower energy level has a frequency directly proportional to the energy change of the electron
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how does quantum mechanics differ from classical mechanics
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classical mechanics adequately describe the motions of bodies much larger than atoms, while quantum mechanics describes the motions of subatomic particles and atoms as waves
