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- Number of protons in an atom - Each element has a unique atomic number - # of electrons in a neural atom |
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- Sum of protons and neutrons - Mass of an atom - Subtract the atomic number from it and you get the number of neutrons in the atom (A-Z= number of neutrons) |
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Two shorthanded notations for the composition of an atom |
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1) Mass number Symbol Atomic number 2) Name of atom-mass# EX: Hydrogen-2 |
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- Atoms with the same number of protons but dif. Number of neutrons - Each element has isotopes |
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Three isotopes of hydrogen |
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1)1/1H (most common) a. Called hydrogen-1 or simply hydrogen 2)2/1H a. Called hydrogen-2 or deuterium 3)3/1 H a. Called hydrogen-3 or tritium |
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Isotopes of an element have |
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1) Different mass numbers 2) Different number of neutrons 3) Same chemical properties because they have the same number of protons and electrons |
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Dalton's Model of the atom |
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- A tiny, indestructable, solid sphere - Had no internal structure |
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Thomson's Model of the Atom |
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- A sphere of positive charge with electrons embeaded in it - Was called the "plum-pudding" model. |
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- student of Thomson - Discovered protons - Carried out a famous gold-foil experiment - Rutherford's Nuclear Model of the Atom ○ Tells us that the atoms is mostly empty space ○ All of the positive charge and most of the mass are in a small region in the center of the atom called the nucleus ○ Nucleus is composed of protons and neutrons ○ Electrons moves around nucleus(outside) |
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- Its existence was predicted by Rutherford. - Has virtually the same mass as a proton, but no change as a proton. - Was discovered by Chadwick. |
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three major subatomic particles: |
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electron, proton and neutron. |
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each proton and neutron is composed of an even smaller particle called a |
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the smallest particle of an element that retains its identity in a chemical reaction. |
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- Was a reek philosopher (460 BC- 370 BC) - Was among the first to suggest the existence of atoms - Believed that atoms were indivisible and indestructible. - Did not carry out experiments |
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