IPC chapter 11- part 3

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what did Ernest Rutherford do?
aimed a beam of small, positively charged particles at a thin sheet of gold foil, found that the particles were deflected or bounced back
nucleus
an atom's central region which is made up of protons and neutrons
what was Rutherford's revised atomic theory?
had electrons circling the nucleus at a distance
Explain Bohr's electron levels:
electrons move around the nucleus in certain energy levels and electrons can jump from a path in one level to a path in another level
electron cloud
a region around the nucleus of an atom where electrons are likely to be found
what substance is about 50000 atoms thick?
aluminum foil
what are negatively charged particles found in electron clouds outside the nucleus?
electrons
what determines the size of the atom?
the size of the electron clouds
which subparticle contains most of the atom's mass?
nucleus
the diameter of the nucleus is :
1/1000000 the diameter of the atom
what are positively charged particles in the nucleus of an atom?
protons
what are particles in the nucleus of an atom that have no charge?
neutrons
what is the SI unit used to express the masses of particles in atoms?
atomic mass unit (amu)
what is the general mass of each proton?
1 amu
what is the unit of mass that describes the mass of an atom or molecule?
atomic mass unit
what are the most massive particles in an atom?
protons and neutrons
is the nucleus dense or not dense?
it is dense
which of the 3 particles is the smallest in mass?
electron, mass is almost 0
how many electrons equal the mass of 1 proton?
1800
explain the charges of protons and electrons?
opposite but equal so their charges cancel out
what happens if the numbers of electrons and neutrons are not equal?
the atom becomes a charged particle called an ion
what happens if an atom loses 1 or more electrons?
becomes a positively charged ion
what happen if an atom gains 1 or more electrons?
becomes a negatively charged ion
how many different elements are there?
more than 110
the number of protons in the nucleus of an atom is equal to what?
the atomic number of that atom
all atoms of an element have the same what?
atomic number
what is an atom that has the same number of protons but different numbers of neutrons?
an isotope
how are isotopes and their atom the same and different?
they are the same element , but have different masses
what is an atom with a nucleus that will change over time?
unstable or radioactive atom
what spontaneously fall apart after a period of time and give off smaller particles and energy?
radioactive atoms
what do isotopes of an element share?
same chemical and physical properties
how can you identify an isotope of an element?
by it's mass number
what is the sum of the numbers of protons and neutrons in the nucleus of an atom?
mass number
what is not included in an atom's mass number?
number of electrons
how many protons and neutrons would hydrogen-2 have?
one proton and one neutron
what would a carbon isotope with the mass number 12 be called?
carbon 12
how do you get the number of neutrons if you know the mass number and the number of protons?
mass number- # of protons = # of neutrons
what do most elements contain?
a mixture of 2 or more isotopes
what is the weighted average of the masses of all the naturally occurring isotopes of that element?
atomic mass
what are the 4 basic forces within the atom?
gravitational force, electromagnetic force, strong force and weak force
what does the amount of gravitational force between objects depend on?
their masses and the distance between them
how do objects with the same charge react to each other?
they repel each other
how do objects with an opposite charge react to each other?
attract each other
what are attracted to each other because they have opposite charges?
protons and electrons
what holds the electrons around the nucleus?
electromagnetic force
what keeps a nucleus with 2 or more protons from flying apart?
the strong force
what is an important force in radioactive atoms?
the weak force; helps a neutron change into a proton or an electron in an unstable atom
the discovery of which particle proved that the atom is not indivisible?
electron
how many protons does an atom with an atomic number of 23 and a mass number of 51 have?
23
In Rutherford's gold-foil experiment, Rutherfrd concluded that the atom is mostly empty space with a small, massive, positively charged center because why?
most particles passed thru foil, some particles were slightly deflected and a few particles bounced straight back
what determines the identity of an element?
atomic number
isotopes exist because atoms of the same element can have different numbers of what?
neutrons