chapter 3 test Flashcards
What happened in the cathode ray experiment?
Investigators noticed when current passed through the tube, the surface of the tube directly opposite the cathode glowed. They discovered that cathode rays were deflected by a magnetic field in the same manner as a wire carrying electric current, which was known to have a negative charge. The rays were deflected away from a negatively charged object. Cathode rays were negatively charged.
Who supported the Cathode ray experiment?
JJ Thompson, he was able to measure the ratio of the charge of cathode ray particles to their mass. Discovered the electrons.
Who measured the charge of the electrons?
American physicist Robert A. Milikan.
What model did Thompson propose?
The plum pudding model (After English dessert). It proposed that the electrons were spread evenly throughout the positive charge of the rest of the atom. It looked like a chocolate chip cookie.
Who provided more detail of the atom’s structure?
Ernest Rutherford.
What experiment did Rutherford and his friends do?
The Gold Foil Experiment.
What did the Gold Foil Experiment entail?
They bombarded the gold thin foil with alpha particles, positively charged. The particles slightly passed through except 1 in 8000 were deflected.
What did Rutherford reason?
The deflected particles must have experienced some powerful force w/in the atom. The force must be caused by a very densely packed bundle of matter w/a positive electric charge (nucleus)
Who did the Bohr Model?
Niels Bohr
Why may two protons be attracted to each other?
When there are two protons are extremely close to each other, there is a strong attraction between them. (nuclear forces).
What are the radii of atoms expressed in?
Picometers
What is the atomic number?
The atomic number is the number of protons of each atoms of that element.
What does the atomic number identify?
An element, if the number of protons were to change so were the elements.
What are Isotopes?
Atoms of the same element that have different masses. The isotopes of a particular elements all have the same number of protons and electrons but different numbers of neutrons.
What is the mass number?
The total number of protons and neutrons that make up the nucleus of an isotope.
What are the two methods for specifying isotopes?
The mass number appears with a hyphen after the name of the element. And the superscript and subscript with the symbol at the end
Is atomic mass a relative measure?
Yes
What is average atomic mass?
The weighted average of the atomic masses of the naturally occurring isotopes of an element.
True or False: Different samples of the same element can differ in their relative abundance of isotopes?
Yes
What is a mole (mol)
The amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12
What is Avogrado’s number?
6.02214179 x 10^23: the number of particles in exactly one mole of a pure substance
What is the molar mass of a substance?
The mass of one mole of a pure substance.
Who is Democritus
Stated that the atomos is uncuttable; you can cut mass down until the atomos
What is the Law of Conservation of Mass?
States that mass is neither created nor destroyed during ordinary chemical reactions or physical changes.
