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ScienceAtomTheory
| Question | Answer |
|---|---|
| In 430 BC, who was the Greek scientist that came up with the idea of atoms? | Democritus |
| Why couldn't the Greeks prove the existence of atoms? | The Greeks did not perform experiments |
| When did the idea of atoms come around again? | 1600s |
| What is the atomic theory? | Series of models developed from experimental evidence |
| Who is John Dalton? | Scientist who proposed atomic theory + model for atoms; inferred that atoms had certain characteristics |
| Summarize the atomic theory. | Elements, composed of atoms, can't be divided; atoms of same ele. alike; atoms of dif. ele. dif.; atom of 1 ele. - can't change into at. of dif. ele., at. can't be created/destroyed, only rearranged; compound - comb. of at. of dif. ele. in set ratio |
| Who found that atoms contained negatively-charged particles, and when? | J.J. Thomson; 1897 |
| T or F: Atoms themselves have electrical charge | false |
| When Thomson found negatively-charged particles, what did he infer? | There must be positively-charged particles to cancel out negatives (since atoms themselves have no electrical charge) |
| Where did Thomson believe the positively-charged particles were located? | Scattered throughout atom |
| Who countered the Thomson model, and when? | Ernest Rutherford; 1911 |
| What experiment did Rutherford conduct to test Thomson's model? | Aimed beam of pos. charged particles @ gold foil; predicted if Thomson was correct, particles would pass through in linear line; gold atoms - not have enough pos. charg. to repel charg. particles, since scattered throughout |
| What were the results of Rutherford's experiment? What did Rutherford infer from the results? | Most particles passed through undisturbed, but some deflected; since like charges repel one another, atom's pos. charges must be clustered in center |
| What did Rutherford call the cluster of positive charges in center of atom? | Nucleus |
| T or F: Atom was mostly empty space in Rutherford's model | True |
| Where is the majority of an atom's mass located? | located in nucleus |
| Do electrons have mass? | no |
| What are the positively-charged particles in nucleus called? | protons |
| Who was Niel Bohr? | Revised atomic model in 1913; showed that electrons could only have specific amounts of energy, causing them to move in only certain orbits. |
| What was revised in the atomic model in the 1920s? | Electrons do not orbit the nucleus like planets, but rather they can be anywhere in a cloudlike region around the nucleus. |
| What is related to an electron's movement? What does this mean? | Electron's energy lvl; electrons of different energy lvls are likely to be found in different places. |
| Who is James Chadwick? | In 1932, he discovered neutrons. |
| Why are neutrons hard to detect? | Neutrons have nearly the same mass as a proton. |
| What does the modern atomic model describe an atom consisting of? | A nucleus containing protons + neutrons, surrounded by a "cloud" of moving electrons. |
| In an atom, what number of particles equals the number of another particle? Why? | The number of protons equals the number of electrons; since the electrical charge of an atom is 0, one proton must be canceled out by one another electron. |
| Does the number of neutrons have to equal the number of protons? Will it affect the charge? | no; neutrons have no effect on the overall charge b/c they have no charge. |
| Does an electron's mass equal to a proton's? | No, electron's mass is 1/1836 the size of a proton's. |
| Does an proton's mass equal to a neutron's? | Approximately. |
| What makes up almost all of the mass in an atom? | Protons + neutrons. |
| What units are used to describe the mass of atoms? | Atomic mass units (amu) |
| How much AMUs does a proton/neutron have? | about 1 |
| What takes up most of an atom's volume? | the space in which electrons move. |
| What is an atomic number? Why is it useful? | Number of protons in nucleus; every atom of an element has the same number of protons. |
| True or False: Every atom of an element can vary in their number of neutrons. | True |
| What are isotopes? | atoms w/ same number of protons but different number of neutrons |
| What are isotopes identified by? | Mass number, the sum of protons + neutrons in nucleus |
| Do all atoms react the same way chemically, even though some of them may have different mass numbers? | Yes |
| Who is Dmitri Mendeleev? | He discovered a set of patterns that applied to all elements; he noticed a pattern of properties when elements are arranged by their atomic mass. |
| What is an atomic mass? | Average mass of all isotopes in an element. |
| What did Mendeleev notice when he arranged the elements by their atomic mass? How did he fix that? | This grouping of elements did not always group similar elements together. He moved some elements to their appropriate groups in effect. |
| When was the periodic table first published? By whom? | 1869 by Dmitri Mendeleev. |
| Who was Henry Moseley? How did his discovery change the periodic table? | In 1913, discovered how to measure positive charges in atom's nucleus (atomic number). Periodic table was then rearranged by atomic number, which provided better groupings of similar elements than atomic mass. |
| Why is the periodic table useful to chemists? | Properties of an element can be predicted based on its location on the table. |
| What are periods in the periodic table? | horizontal rows, left + right ends have most highly reactive elements, w/ exception of nonmetals to right. |
| What are the lanthanides + actinides? | Periods 6 and 7 of the table. |
| What are groups in the periodic table? | vertical columns, consists of elements w/ similar characteristics |
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Mindsweeper
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