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chapter 4 science

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Who was Democritus?
a greek philosopher that gave atoms the name 2000 years ago.
What are atoms?
smallest part of an element
What are the 4 steps of Daltons atomic theory?
1. all elements are composed of tiny individual particles called atoms
2. atoms of the same element are identical
4. chemical reactions occur when atoms are separated, joined, or rearranged
What happens if atoms have only one element?
they are never changed into atoms or another element as a result of a chemical reaction.
What did J.J Thomson use to discover electrons?
cathode ray tube
What model did J.J Thomson use?
the plum pudding model
What did J.J Thompson find out by adding an electric field?
he found that moving pieces were negative
What did Rutherford find out about atoms?
he found out that atoms had a positive charge concentrated in the nucleus
What was Rutherford's model?
the planetary model of atoms
What were Rutherford's conclusions?
1. atoms are mostly empty space
2. all the positive charge and almost the mass of an atom are concentrated in the nucleus
3. nucleus-tiny central core of an atom composed of protons and neutrons
4. electrons are distributed around the nucleus and occupy almost all the volume of the atom
What are the three subatomic particles?
protons, electrons and neutrons
What is a Proton?
is positively charged and found in the nucleus of an atom
What is a Electron?
negative charge found outside of the nucleus charge of negative
What are Neutrons?
neutral charge in the nucleus
What is the electrons charge and relative mass?
its charge is +1 and its relative mass is 1/1836
What is protons charge and relative mass?
its charge is +1 and its relative mass is 1
What is neutrons charge and relative mass?
its charge is 0 and its relative mass is 1
What makes up the atomic mass of an atom?
protons and neutrons
What is the atomic number?
the number of protons in an element
How do you find the number of neutrons in an atom?
Atomic mass - Atomic number = number of neutrons
What are Isotopes?
atoms of the same element that have different numbers of neutrons and different mass numbers.
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