Chem quiz 1

Dalton's atomic theory

1. Matter is composed of indivisible particles.

2. Atoms of the same element are identical in mass and properties.

3. Atoms cannot be created or destroyed in chemical reactions.

4. Compounds are formed by combining atoms in fixed ratios.

5. Chemical reactions involve the rearrangement of atoms.

cathode ray tube

Cathode Ray Tube (CRT)

A cathode ray tube is a vacuum tube that contains one or more electron guns and a phosphorescent screen. It was widely used in older television sets and computer monitors. The electron guns emit beams of electrons that are directed towards the screen, where they create images by illuminating phosphor coatings. CRTs have largely been replaced by flat-panel displays like LCD and LED due to their bulkiness and lower energy efficiency.

gold foil experiment

Gold Foil Experiment

The gold foil experiment, conducted by Ernest Rutherford in 1909, demonstrated that atoms have a small, dense nucleus. Key points include:

• Setup: Alpha particles were directed at a thin foil of gold.

• Observations: Most particles passed through, but some were deflected at large angles.

• Conclusion: Atoms consist mostly of empty space, with a small, positively charged nucleus at the center, leading to the nuclear model of the atom.

bohr

• Electrons occupy fixed orbits with quantized energy levels.

• Energy is emitted or absorbed when an electron moves between these orbits.

• The model explains the spectral lines of hydrogen.

propability model

Probability Model

A probability model is a mathematical representation of a random phenomenon. It consists of:

1. Sample Space (S): The set of all possible outcomes.

2. Events: Subsets of the sample space.

3. Probability Function (P): Assigns a probability to each event, satisfying:

   • (0 \leq P(E) \leq 1) for any event (E)

   • (P(S) = 1)

   • For mutually exclusive events, (P(A \cup B) = P(A) + P(B)).

Common types include discrete and continuous probability models.