| PEOPLE | MODELS | ATOMIC THEORY | PERIODIC TABLE | ATOMS AND IONS |
|---|---|---|---|---|
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Who proposed the first scientific atomic theory?
English chemist John Dalton
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What does Dalton’s model look like?
As a smooth solid sphere, without an electrical charge
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When did John Dalton propose his theory?
In 1808
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What does the ion charge of an element tell you?
How many electrons the atom lost or gained
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What happens when an atom forms an ion?
It either gains extra electrons and becomes negatively charged, or it loses electrons and becomes positively charged
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Who discovered the electron?
J.J. Thomson
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Why is J.J. Thomson’s atomic model called the “raisin-bun” model?
Because the negatively charged electrons are randomly scattered in a positively charged matter
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Why are metal-nonmetal compounds not molecules?
Because metal-nonmetals technically do not have molecules
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How do you find the number of neutrons in an atom?
Atomic mass (rounded) minus atomic number.
Example: 27 - 13 = 14 (Aluminum) |
Do noble gases normally form ions? Why?
No, because they already have enough electrons to fill all their shells (stable)
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Who revised the atomic theory in the 1830s?
Michael Faraday
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why do the electrons “jump” and fall back between shells?
The electrons move between shells because they are heated or approached by high currents of electricity
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When was the electron discovered?
In 1898
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What changes in an atom when it forms an ion?
The number of electrons orbiting the nucleus changes
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Why are group 1 and 17 very reactive?
Because they easily give up one electron (group 1) or gain one electron (group 17)
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What is the relationship between J.J. Thomson and Ernest Rutherford?
Rutherford was a former student of J.J Thomson’s
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What is Rutherford’s model called and what is the main difference between Rutherford’s model and previous models?
The nuclear model of the atom, Rutherford added the idea of a nucleus in the atom, and orbits of electrons
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What did Bohr propose in his atomic theory?
The electrons are restricted to specific “allowed” orbits (shells) around the nucleus
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What does the atomic mass of an element represent?
The average of mass numbers of all the naturally occurring isotopes
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How are molecular compounds formed?
They are formed due to the electron sharing between two or more atoms
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Who used the emission spectrum of elements to solve the problems with Rutherford’s model of the atom?
Niels Bohr (former student and colleague)
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According to Bohr’s model, why do we see emission spectrums?
We see the spectrums because of the energy caused by electrons moving(jumping & falling back) between defined shells
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According to Bohr’s theory, what is the difference between an Ionic bond and a covalent bond?
An ionic bond forms when a metal atom transfers electrons to a non-metal atom. They are held by electrical force.
A covalent bond forms when two non-metal atoms share their electrons |
What are the four ways of classifying the elements?
By their physical properties, by family, by groups, and by atomic number
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How are ionic compounds formed?
When a nonmetal atom and metal atom transfer electrons with each other, the atoms become ions and are held together because of electrostatic force
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