What particle did J. J. Thompson discover?
Electrons
How would you describe the nucleus? (include place, size compared to atom, made of what, and what charge doe it have?)
Center of atom, small compared to atom, made of protons and neutrons, positive charge
Where are electrons likely to be found?
In electron clouds
Dalton believed that atoms of the same element are?
identical; exactly the same
Every atom of a given element has the same number of_________.
protons
What is the meaning of the word atom?
Uncuttable
Which statement is true about isotopes of the same element?
They have different numbers of neutrons but the same number of protons.
What did Rutherford believe was in the center of the atom?
the nucleus
what did Democritus, Thomson, Rutherford, and Bohr all have in common?
they all contributed to atomic theory
In the plum-pudding model, the plums represent
electrons
An atom of gold with 79 protons, 79 electrons, and 118 neutrons has a mass number of
197
Which of the following has the least mass?
A. Protons
B. Electrons
C. Nucleus
D. Neutrons
B
If an isotope of uranium, uranium-235, has 92 protons, how many protons does the isotope uranium-238 have?
92
What is the smallest particle into which an element can be divided and still be the same substance?
atom
Who proposed the plum-pudding model?
J. J. Thompson
A carbon with 6 protons, 6 electron, and 6 neutron would have a mass number of
12
In an atom, which has the most mass?
A. Nucleus
B. Protons
C. Electrons
D. Neutrons
A
In 1803 John Dalton proposed that all substances are made of __________.
atoms
Scientists now believe electrons are found in regions called
electrons
Neutrons and _______ each have a mass about 1 atomic mass unit.
Protons
Because the mass of a(n) ________ is so small, it is usually thought of as almost zero.
Electron
Isotopes have different numbers of ___________.
Neutrons
The sum of the protons and neutrons in an atom is called the__________.
Atomic mass number
Around 440 BCE, Democritus proposed the idea of a(n) _________ particle that could not be cut in half.
atom
In 1911, Ernest Rutherford proposed that each atom has a(n) _____________, a tiny, extremely dense, positively charged region.
nucleus
Most of the atom's mass is found in the
nucleus
All atoms of an element have the same
atomic number
The current atomic theory includes the ______________ model.
plum pudding
The smallest units of an ___________ are atoms.
element
Most elements have a mix of two or more___________.
isotopes
Protons stay together in the nucleus because of the__________.
strong force
Electrons around the nucleus are held together by the__________.
Electromagnetic force
A positively charged particle in the nucleus of an atom is___________.
Proton
An atom of an element that has the same number of protons but different neutrons is called a(n)_________.
Isotope
The region in an atom that contains most of the mass is called the______________.
nucleus
The number of protons in an atom determines its________.
atomic number