Blue (200 points)
Elements that are mostly formed during the Big Bang.
Hydrogen & Helium
What process happens in stars that turns hydrogen into helium?
Nuclear Fusion
A process that creates heavier elements in stars.
Nucleosynthesis
The first Greek philosopher to propose the idea of the atom.
Democritus
According to Democritus, how could atoms be described?
They were invisible, solid, and indivisible
What are the three main subatomic particles found in an atom?
Neutrons, protons, and electrons
Who's discovery has first challenged the idea that atoms were indivisible?
J.J Thompson
Which scientist proposed that electrons move in specific orbits or energy levels?
Neil's Bohr
His discovered that the atomic number (number of protons) is the correct basis for organizing the periodic table, not atomic mass.
Henry Mosely
A certain element has an atomic number of 7 and a mass number of 10. How many neutrons does this element have, assuming it’s a neutral atom?
3
What did Rutherford’s gold foil experiment prove about the atom?
The atom has a dense, positively charged nucleus
What does the atomic number of an element represent?
#of Proton
How has knowledge of atomic number helped scientists create new elements?
By adding protons
Carbon-12 and Carbon-14 is an examples of?
Isotopes
What is the main reason a molecule becomes polar?
There is an unequal distribution of electrons
Which of the following is most likely a nonpolar molecule?
A. NH₃ (ammonia)
B. CH₄ (methane)
C. H₂O (water)
D. SO₂ (sulfur dioxide)
B
Why do polar molecules usually have higher boiling points than nonpolar molecules?
They have stronger intermolecular forces
Which of the following best explains why water (H₂O) can dissolve many substances?
. It is polar and can form hydrogen bonds
What is the strongest type of intermolecular force?
Hydrogen bonding
Dipole-dipole interactions occur between:
Polar molecules with permanent dipoles
According to collision theory, what must happen for a chemical reaction to occur?
Particles must collide with enough energy and proper orientation
How does increasing the concentration of reactants affect the rate of reaction
It increases the number of collisions between particle
How does smaller particle size affect the reaction rate?
It increases surface area, leading to more frequent collisions
. A substance that increases the reaction rate without being used up
Catalyst
How does a catalyst increase the rate of a chemical reaction?
By lowering the activation energy needed for the reaction