History of Atomic Models
This Greek philosopher proposed that matter was made of tiny, indivisible particles called atomos.
Democritus
A particle has a +1 charge and is found in the nucleus. Identify it.
Proton
Write the hyphen notation for an atom of carbon with a mass number of 12.
Carbon-12
What makes two atoms isotopes of the same element?
Same number of protons, different numbers of neutrons.
A scientist discovers negatively charged particles inside atoms. Which scientist's work does this support?
Thomson
Dalton used these ideas to develop the first modern atomic theory.
Atoms are the basic particles of matter.
A particle has no charge and is found in the nucleus. Identify it.
Neutron
An atom is written as ²³₁₁Na. What is its atomic number?
11
Carbon-12 and Carbon-14 have the same number of what particle?
Protons
An experiment shows that atoms are mostly empty space. Which scientist's experiment?
Rutherford
Thomson's cathode-ray experiment showed that atoms contain what particle?
Electrons
An atom has 11 protons, 12 neutrons, and 11 electrons. What is its mass number?
Write the isotope symbol for an atom with 17 protons and 18 neutrons.
³⁵₁₇Cl
Carbon-12 has 6 protons. How many neutrons does it have?
6
A model shows electrons moving in specific energy levels around the nucleus. Which scientist?
Bohr
Rutherford's gold-foil experiment showed that most of an atom is what?
Empty space
An atom has 17 protons and 18 electrons. Is it positive or negative, and what is its charge?
Negative, −1
Write the isotope symbol and hyphen notation for an atom with 8 protons and 10 neutrons.
¹⁸₈O; Oxygen-18
Carbon-14 has 6 protons. Compare its neutrons and mass to Carbon-12.
Carbon-14 has 8 neutrons and a greater mass.
A scientist claims atoms are solid, indivisible spheres. Later, electrons are discovered. Which scientist's model must be revised?
Dalton
Rutherford expected alpha particles to mostly pass through the foil. Some bounced back. What did this reveal?
Atoms have a small, dense, positively charged nucleus.
An atom has 20 protons, 20 neutrons, and 18 electrons. Determine its mass number and charge.
Mass number = 40; charge = +2
An atom is written as ⁴⁰₂₀Ca. Give its element, atomic number, mass number, protons, and neutrons.
Calcium; 20; 40; 20 protons; 20 neutrons
Two atoms have 17 protons. Atom A has 18 neutrons, and Atom B has 20. Identify both isotopes.
Chlorine-35 and Chlorine-37
Experiment: Most particles pass straight through a thin sheet of gold, but a few are strongly deflected. What two conclusions can be made about the atom?
Most of the atom is empty space, and it has a small, dense, positively charged nucleus.