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22 Cards in this Set
- Front
- Back
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Democritus's atomic philosophy |
Democritus believed that atoms were indivisible and indestructible |
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What did Dalton do with Democritus's theory? |
Using experimental methods, Dalton transformed Democritus's ideas on atoms into a scientific theory. |
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Dalton's atomic theory |
1. All elements are composed of tiny indivisible particles called atoms 2. Atoms of the same element are identical. All element's atoms are different from one another. 3. Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds. 4. Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction. |
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How do people view single atoms? |
Despite their small size, individual atoms are observable with instruments such as scanning tunneling microscopes. |
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What is the range of the radii of most atoms? |
5 x 10 (-11) m to 2 x 10 (-10) m |
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What are the three kinds of subatomic particles? |
Electrons, Protons, and Neutrons |
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How did the cathode ray experiment work? |
The current that passed through a tube was attracted to positive plates and repelled by negative plates, so J J Thomson hypothesized that there were negatively charged particles (electrons). |
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What did the US physicist Robert A. Millikan do? |
He carried out experiments to find the quantity of charge carried by an electron. (He calculated the mass of an electron) (1/1840 the mass of a hydrogen atom) |
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What did Eugen Goldstein do? |
He found rays traveling in the direction opposite to that of the cathode rays. Then, he concluded that these were positive particles and called them protons. |
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What did James Chadwick do? |
He confirmed the existence of the subatomic particle the neutron. |
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What is J J Thomson's Plum Pudding model? |
In his model, electrons were stuck into a lump of positive charge, similar to raisins stuck in a dough. |
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What did Ernest Rutherford do? |
He made the gold foil experiment. The gold foil experiment was basically Rutherford shooting alpha particles directed at a very thin sheet of gold foil. Instead of a deflection, the majority of alpha particles went straight through, and a small fraction bounced off at strange angles. |
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What did Rutherford conclude? |
He proposed that atoms are mostly empty space and that all the positive charge and most of the mass is concentrated in a small region. |
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What is Rutherford's atomic model? |
Rutherford's atomic model, the nuclear atom: Protons and neutrons are located in the nucleus. The electrons are distributed around the nucleus and occupy almost all of the volume of an atom. |
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How are elements different? |
Elements are different because they contain different numbers of protons. |
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How can you find the number of electrons? |
Because the atomic number is the number of protons, and the charges in an atom have to be balanced, the number of electrons is the atomic number (or the number of protons). |
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How do you find the number of neutrons? |
The number of neutrons in an atom is the difference between the mass number and the atomic number. |
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Where is the mass number, atomic number, and name of the element located in shorthand notation? |
The mass number is above the atomic number, and they are both on the left of the element name. |
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Why do isotopes have different mass numbers? |
Because isotopes of an element have different numbers of neutrons, they also have different mass numbers. |
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What makes the periodic table such a useful tool? |
A periodic table allows you to easily compare the properties of one element to another element. |
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From periods and groups, which one has similar properties? |
Groups |
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How is atomic mass calculated? |
To calculate the atomic mass of an element, multiply the mass of each isotope by its natural abundance (percent), then add the products. |
