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Atomic Structure & the Periodic Table

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Law of Conservation of Mass
During a chemical reaction, the total mass of the reactants is always equal to the total mass of the products
Law of Definite Proportions
a given compound always contains exactly the same proportion of elements by mass
Law of Multiple Proportions
If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is alwa…
Atomic Mass Unit
A unit of mass that describes the mass of an atom or molecule. (amu)
Atomic Number
A unique number for each element on the periodic table that is equal to the number of protons in any atom of that element. 2. The elements Identity
average atomic mass
The average of the atomic masses for the isotopes of an element.
atoms of the same element that have different masses: the same protons, but different neutrons -same chemical properties
mass number
Sum of protons and neutrons
Avogadro's Number
6.02 x 10²³ particles
_______is the amount of a substance that contains the same number of particles as the number of atoms in 12 g of carbon-12. That would be 6.02 x 10 23 atoms.
electromagnetic energy
energy that travels through space in forms of waves
How many waves can pass a given point per second, measured in Hertz (Hz).
Length of the wave
the amount of energy needed to move an electron from one energy level to another
A particle of electromagnetic radiation with no mass that carries a quantum of energy
line emission spectrum
A series of specific wavelengths of emitted light created when the visible portion of light from excited atoms is shined through a prism
A region of space around the nucleus where an electron is likely to be found.
Basic building block of all matter.
a proton is located in the _______ of an atom
A negatively charged subatomic particle located in the electron cloud outside the nucleus. It determines how atoms combine with other atoms.
excited state
A state in which an atom has a higher potential energy than it has in its ground state
electron configuration
Arrangement of electrons in an atom
periodic law
physical and chemical properties of the elements are a periodic function of their atomic numbers (number of protons in the nucleus); -elements with similar properties occur at regular and predictable intervals (medeleev)
Periodic Table
A chart of the elements showing the repeating pattern of their properties
atomic radius
A measure of the size of an element's atoms; usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons.
Ionization Energy
Energy needed to remove an electron from the valence shell of an atom - how easily an atom can become an ion (COMPARE REACTIVITY OF A METAL)
valence electrons
an electron in the highest occupied energy level of an atom;available to be lost, gained, or shared in the formation of chemical compounds
Electron Affinity
Energy emitted upon addition of an electron - tendency to gain an electron (COMPARE REACTIVITY OF A NONMETAL)
a measure of the ability of an atom in a chemical compound to attract electrons
A charged atom
thomson atomic model
plum pudding - atom was a positively charged solid mass (pudding) which has negatively charged electrons stuck to it. (plums)
Rutherford atomic model
Rutherford concluded that the atom is mostly empty space. All the positive charge and almost all of the mass are concentrated in a small region called the nucleus
Bohr atomic model
Atoms described as electrons orbiting the nucleus in well defined paths (solar system model), electrons can jump paths
modern atomic model
atom consists of a nucleus that contains protons and neutrons surrounded by an electron cloud
(460-370 BCE) A Greek philosopher who theorized that all matter could be reduced to particles that could not be divided, which he described as "atomos."