Atomic Structure and Periodicity

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Atom
the smallest particle of an element that retains its identity
Element
simplest form of matter that has a unique set up of properties
What was Daltons experiment
The sizes of the particles making up different gases must be different, Dalton realized that different particle sizes mean different structures
What was Dalton’s first Atomic Theory
Smallest particle of any element is the atom, which is indestructible.
Why was Dalton’s first Atomic theory false
-Subatomic particles- electrons, protons and neutrons
-High-energy physics and nuclear reactions show we can break atoms down into their subatomic particles
What was Dalton’s second atomic theory
All atoms of a given element are identical
Why is Dalton’s second atomic theory false
-Not all atoms of the same element are identical
-Many atoms have different versions of themselves-isotopes-which differ in atomic weight and composition
What was Dalton’s third atomic theory
Chemical compounds result from combinations of two or more atoms of different elements in simple whole number ratio
Why was Dalton’s atomic theory true
Law of Definite compositions
Law of Definite Composition
all samples of a pure compound, no matter the source, always contain the same elements in the same non-changing ratios by mass
What was Dalton’s fourth atomic theory
Atoms of the same elements can combine in two or more different ratios to form two of more different compounds
Why was Dalton’s fourth atomic theory true
Law of Multiple Proportions
Law of Multiple Proportions
elements in a compound, however many there are, always combine in a fixed, definite mass ratio
J.J. Thomson
discovered the three basic kinds of subatomic particles
What is the Crookes tube experiment
Thomson constructed the experiment, allowed an electric current to pass through a gas sealed in a glass tube at very low pressure
What is the mass of a hydrogen atom
1/1840
What is the smallest type of subatomic particle
electrons
What is the largest type of subatomic particle
protons and neutrons
Protons
positively charged particle in an atom with a calculated about 1840 times that of an electron
Neutrons
subatomic particle with no charge – neutral. Has a mass nearly equal to a proton
Atomic mass unit
(amu)
-1 amu + 1.6606x 10-24 g
Ernest Rutherford
confirmed the plum pudding model, confirmed the existence of the nucleus
What type of experiment did Rutherford design
The gold foil experiment
What was Rutherford’s profound conclusion
Electrons move around the nucleus, much like planets around a sun, resulting in a negatively charged cloud-like region
What do electrons occupy
region known as the electron cloud
What is the size of an electron cloud
10,000-20,000 times the size of the nucleus
Atomic number
number of protons
what equals the number of electrons
protons
Mass number
number of protons + number of neutrons in the nucleus of an atom
Number of neutrons equals
mass number – atomic number
what does the atomic number determine
the chemical properties of an atom
what does the mass number help determine
the number of neutrons, but neutrons play no role in creating chemical bonds
why wouldn’t the number of neutrons always equal the number of protons
we call the different versions of the same atom isotopes
isotopes
two atoms of the same element that differ in the number of neutrons
isotopic form
the different isotopes of an element
why do isotopes exhibit the same chemical behaviors as the normal atom
the number of protons and electrons do not change
percent natural abundance
percentage distribution of the isotopes of an element
Dalton
another term for amu
what is the electron mass
1/2,000th of neutron or proton
when is the electron mass ignored
when totaling mass of atom
how to calculate a weighted-average of the atomic mass
1. convert the percent natural abundance of each isotope into a decimal number – by diving each by 100%
2. multiply atomic mass of each isotope by the decimal equivalent of its natural abundance
3. sum the atomic masses of the isotopes
ion
atoms which gain, or lose, an electron during a chemical reaction
what happens when a atom loses one of its negatively
its overall electrostatic charge becomes positive
what happens when a atom gains one of its negatively
its overall electrostatic charge becomes negative
are ions still the same element
the number of protons did not change
anion
negatively charged ions and nonmetals
cation
positively charged and metals
monatomic ions
forms from a signal atom
Categories: Atomic Physics