Subatomic Particles
What subatomic particle has a positive charge?
Protons
What is found in the nucleus of an atom?
Protons and Neutrons
Who discovered the electron using a cathode ray tube?
J.J. Thomson
What do all isotopes of an element have in common?
The same number of protons
Which subatomic particle has the least mass?
Electron
Which particle orbits the nucleus in energy levels?
Electron
How do you calculate the mass number of an atom?
# of Protons + # of Electrons
Which scientist proposed that atoms are mostly empty space?
Ernest Rutherford
What is the charge of an ion that has more electrons than protons?
Negative (anion)
What is the charge of a neutron?
neutral (0)
What is the mass of a neutron in atomic mass units (amu)?
What determines the identity of an atom?
The number of Protons
What was Dalton’s main contribution to atomic theory?
All matter is made of indivisible atoms
An atom of carbon has 6 protons and 7 neutrons. What is its mass number?
13
What term is used for atoms of the same element with different numbers of neutrons?
Isotopes
Which particle determines the reactivity of an atom?
Electron/Valence electron
An atom is neutral. If it has 15 protons, how many electrons does it have?
15
What model did J.J. Thomson propose for the atom?
Plum Pudding Model
What does the term “isotope” mean in terms of atomic structure?
Same element, different number of neutrons
Which element has 1 proton?
Hydrogen
Rank the three subatomic particles from least to greatest mass.
Electron < Proton ≈ Neutron
If an atom has 20 protons, 21 neutrons, and 18 electrons, what is its net charge and mass number?
+2 Charge, 41 mass number
Which experiment led to the discovery of the nucleus?
Rutherford’s Gold Foil Experiment
A calcium ion has 20 protons and 18 electrons. What is its symbol with charge?
Ca2+
Why are atoms considered mostly empty space?
Because electrons are very far from the nucleus relative to their size