quiz on slides Flashcards
All elements are composed of tiny particles called atoms. true or false:
True
Atoms of the same element are identical. The atoms of any one element are different from those of any other element. true and false:
False
Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds. true or false:
True
Chemical reactions occur when atoms are separated from each other, joined, or rearranged in different combinations. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction. true or false:
True
Key features of the Cathode Ray Tube Experiment
- Deflected by electrically charged metal plates
- Positively charged plate = attracts cathode ray; negatively charged plate = repels cathode ray
- Deflected by magnets
Describe the key features of the plum pudding model.
- Proposed by J.J. Thomson in 1904
- Explains two properties of atoms: Electrons are negatively charged particles
- Atoms have no net charge
- Electrons surrounded by a volume of positive charge
- Negatively charged “plums” in a positively charged “pudding”
- The positive matter was thought to be jelly-like, or similar to a thick soup
- The electrons were considered somewhat mobile
Results of the Gold Foil Experiment
most α particles went straight through the gold foil some slightly deflected. However,a small number of the α particles bounced off the gold foil at a very large angle.(like particles reflect)
what is the Gold Foil Experiment also known as
Also known as Geiger–Marsden experiment
what is the Gold Foil Experiment
It is a scattering experiment designed and researched by a team led by Ernest Rutherford. It successfully confirmed that there is a nucleus in the center of the atom in 1909, which also led to the creation of the Rutherford model (planetary model) and later Bohr’s Proposal of the model, Rutherford Atomic Model
Describe the key features of Rutherford’s model
- Atoms consists of a positively charged nucleus
- Negatively charged electrons orbits the nucleus (planetary electrons)
- The nucleus contains most of the mass of the atom
- The electrons (despite their negative charge) have very little mass in relation to the nucleus
- The atom is electrically neutral, with the positive charge of the nucleus balanced by the negative charge of the electrons.
- Electrons occupy some of the energy levels (the shells) in the nucleus
Bohr Model of the Atom
- It has a nucleus
- The model has 3 electron rings
based on the Hydrogen Atom - Electrons orbit the nucleus in orbits that have a set size and energy.
- The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.
- Radiation is absorbed or emitted when an electron moves from one orbit to another.
The Millikan Oil Drop Test
- Oil droplets were sprayed into the chamber and the oil droplets which were atomized.
- Oil droplets become charged randomly when sprayed through the atomizer due to friction with the nozzle.
- Made oil droplets hover by adjusting the electric charge of the metal plates
- 2 metal plates (Top plate positive charge, Bottom plate negative charge)
- Negative charged droplet move to top plate while negative move to bottom plate
- Calculate: Knowing the strength of gravity, the size of the droplet, and the electric force needed to make the droplet hover, they could work out the charge on that droplet.
- Observe using viewing scope (which plate oil droplets moves towards)
Similarities of the plum pudding, Rutherford’s, and Bohr’s models
- The Rutherford model and the plum pudding model both acknowledge the existence of positively and negatively charged material within the atom
- Rutherford and Bohr’s models both denote that electrons orbit the nucleus
- Both the Plum pudding and Bohr models maintain that the overall charge of an atom will stay neutral.
- All models acknowledge that negatively charged electrons exist within the atom
- All models acknowledge that positively charged material exists within the atom
- All models acknowledge that densely packed nuclei exist within the atom
Differences among plum pudding, Rutherford’s, and Bohr’s model
Plum pudding and Rutherford’s models
- Rutherford said that the protons and neutrons were located in a positively charged nucleus and the electrons are distributed around the nucleus.
- In the plum pudding the electrons and positively charged matter are in a neutrally charged nucleus.
- Rutherford’s model also states that the Nucleus is tiny and densely packed compared with the atom as a whole
Rutherford and Bohr’s models
- Bohr’s had a fixed orbit around the nucleus
- Rutherford did not have neutrons but just a tiny positively charged nucleus
- Rutherford’s model’s electrons did not have a set path like Bohr’s
Plum pudding and Bohr’s models
- The plum pudding model has the electrons inside of a densely packed neutral-charged nucleus
- Bohr’s model has electrons in a fixed orbit around a positively charged nucleus
- They orbit the nucleus similarly to how a planet orbits the sun
symbols of the particles
p+
e-
n0
