Question | Answer |
What did Democritus call natures best particle of an atom? | indivisible and indestructible |
Who was the english chemist and teacher that formulated theory to describe structure and chemical reactively of matter in an atom? | John Dalton |
What is an atom? | elements composed of tiny particles that retains its identity in a chemical reaction |
In what type of ratios do atoms combine to form compounds? | Atoms of different elements can physically mix together or chemically combine in simple whole-number ratios |
Who was the Greek philosopher among the first to suggest the existence of atoms? | Democritus |
What does John Dalton's Modern Atomic Theory state? | atoms are divisible and an element can have atoms with different masses |
What did John Dalton propose? | elements were composed of atoms and only whole-number of atoms can combine to form compounds |
Why can Dalton's ideas be called a theory? | He changed Democritus' ideas into a theory that could be tested. |
What is the nucleus? | the central core of an atom |
Which subatomic particles are in the nucleus of an atom? | protons and neutrons |
What are the three subatomic particles? | protons, neutrons, and electrons |
What was Rutherford's atomic model? | "nuclear atom" |
Who discovered the neutron (other component of the nucleus) in 1932? | James Chadwick |
Which subatomic particle occupies most of the volume of the atom? | Electron |
What is a cathode ray? | stream of electrons produced at the negative electrode of a tube containing a gas at low pressure |
What did Democritus believe about atoms? | they physically resembled the matter it made (rock atoms were sharp and jagged, fur atoms were soft and fuzzy) |
What do the "anatomy" af an atom have? | a nucleus and electron could |
Who discovered the electron? | J.J. Thomson |
How did J.J. Thomson know the ray was composed of negatively charged particles? | the particles deflected by a magnetic field in the same way as a wire carrying an electrical current |
What does the presence of a negatively charged particle within a neutral structure (atom) have a indication of? | negatively charged particles moving up the cathode ray |
What does the very small mass of the electron compared to the relatively large mass of an atom indicate? | there is probably a positively charged particle in the atom that has more mass than the electron |
What is Thomson's atomic model? | 'plum pudding' |
When Ernest fired the alpha particles through a thin piece of gold foil, what did he expect the particles to do? | deflect |
What actually happened with the most of the alpha particles? | they went straight through the gold foil undeflected |
What actually happened with the other alpha particles? | some: were deflected
few: bounced back at large angles |
Why could Rutherford conclude that the atom is mostly empty space? | some alpha particles went through |
Why could Rutherford conclude that there was a small, dense, area of positive charge? | some particles were deflected |
What did Thomson detect that the electron has? | a certain amount of negative charge per unit of mass |
What does Thomson's 'Plum Pudding' not have? | a nucleus and neutrons |
What is the atomic number? | # of p+ and e- in each atom of that element |
How are elements different from one another? | they have different #s of protons |
What is the mass number? | total # of p+ and neutrons in nucleus. |
What is the atomic mass? | weighted average mass of the atoms in a naturally occurring sample of an element |
How do you find the # of neutrons? | atomic number - atomic mass (rounded) |
If the atom is neutral (no charge) then what does it have? | the same # of e- |
What are neutrons? | subatomic particle that has no charge but has a mass nearly equal to that of a proton |
What are electrons? | subatomic particle that are negatively charged |
What are protons? | subatomic particle that is positively charged |
What does I amu equal? | 1/12 the mass of a carbon-12 atom |
What would you do to calculate atomic mass? | 1. Multiply the mass of each isotope by its % natural abundance (in decimal form, rounded 2 to the left)
2. Add the answers |
What are atoms of the same element that have different masses (different amounts of neutrons)? | isotopes |
How is (nuclear notation) expressed? | mass # on top, element, atomic # on bottom |
How is hyphen notation expressed? | element-# #of p+ and neutrons |
What is a periodic table? | an arrangement of element where the elements are separated into groups based on a set of repeated properties |
What is a group? | each vertical column in the periodic table |
What is a period? | each horizontal row of the periodic table |