Chemistry: Atoms

Niat Habtemariam
Flashcards by Niat Habtemariam, updated more than 1 year ago
Niat Habtemariam
Created by Niat Habtemariam almost 7 years ago
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High School Diploma Science Flashcards on Chemistry: Atoms, created by Niat Habtemariam on 08/26/2014.

Resource summary

Question Answer
The Law of Conservation of Mass: Mass is neither created nor destroyed during ordinary chemical reactions or physical changes. (Ex.) The total mass of reactants will always be equal to the total mass of products in any reaction.
The Law of Definite Proportions: A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound. (Ex.) Table Salt is exactly 39.34% sodium and 60.66% chlorine by mass.
The Law of Multiple Proportions: If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.
Dalton's Model of an Atom
How was Dalton's model useful? This model was used as a base for all other atomic discoveries and atomic models.
What was Dalton's Theory of Matter? 1. All matter is composed of extremely small particles called ATOMS. 2. ATOMS of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties. 3. Atoms cannot be subdivided, created, or destroyed. 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. 5. In chemical reactions, atoms are combined separated, or rearranged.
What aspects of Dalton's theory have been proven incorrect? ♦ Atoms are divisible into smaller particles. (protons, neutrons, electrons, quarks, etc.) ♦ A given element can have different masses. (Isotopes)
Thompson's Model of an Atom
How was Thompson's model useful? This model of the atom introduced positive and negative charges in an atom.
How can Thompson's model be misleading? His model doesn't include neutrons in his model. Meaning that there weren't isotopes of atoms.
What experiment did Thompson do that led him to the discovery of the electron? The Cathode-ray experiment
What happened in the Cathode-Ray experiment? A stream of particles flows through gas when an electrical charge is passed through it. Researchers notice that the stream of particles moves away from a negatively-charged plate.
What was Thompson's Conclusion in his Cathode-Ray Experiment? ♦ Because atoms are neutral, they must contain a positive charge to balance the negative electrons. ♦ Because electrons have so much less mass than atoms, atoms must contain other particles that account for most of their mass.
What experiment did Rutherford do that led him to the discovery of the Atom's nucleus? Gold Foil Experiment
Why did some of the particles from the Gold Foil Experiment deflect back while most didn't? The particles that had went straight through the gold foil had went through the empty space of an atom. The few that were deflected back had hit the nucleus of an atom. This shows that atoms are mostly made of empty space.
What was the conclusion of Rutherford's experiment? There must be a very densely packed bundle of matter with a *positive electric charge* in each atom. (This "bundle would be the size of a marble in the middle of a football field)
Rutherford's Model of the Atom
How is the Rutherford's model useful? Rutherford's model introduced the discovery of a dense, positively charged nucleus. It also proved that an atom is composed of mostly empty space.
Bohr's Atomic Model
What is Nuclear Force? The unusually strong forces that hold protons and neutrons together in the atomic nucleus. (It is what holds the protons together despite their same positive charges).
The Quantum Model
Why was Bohr's model misleading? Bohr was incorrect in assuming that electrons moved like planets in a solar system.
How was Bohr's model useful? Bohr was correct in his findings that Electrons has different energy levels and that Electrons can gain and lose energy.
How was Rutherford's model misleading? Rutherford was incorrect in stating that electrons move randomly around the space in the nucleus.
What is a Mass Number? The number of protons and neutrons in an element's nucleus.
What is the Atomic Number? The number of Protons of each atom in an element.
Nuclear Symbol
Hyphen Notation
What is the Average Atomic Mass? The weighted average of the atomic masses of the naturally occurring isotopes of an element.
Avagadro's Number 6.022 x 10²³ is exactly how many things are in 1 mole of a substance
What is molar mass? The mass of one mole of a pure substance is called the molar mass of that substance.
What do scientists use to detect isotopes of various elements and determine their relative abundances? A Mass Spectrometer.
How is molar mass measured? In units of grams/moles. Ex. 12.01 g/mol
List the Four Quantum Numbers and the specific information about atomic orbitals they provide: 1. Principle Quantum Number -tells which energy shell the electron occupies 2. Angular Momentum Quantum Number- shape of orbital 3. Magnetic Quantum Number- Orientation of orbitals around the nucleus 4. Spin Quantum Number- (+1/2) for clockwise and (-1/2)
What is the relationship between wavelength and frequency? The higher the frequency, the shorter the wavelength.
How is light like a particle? Light energy is found at discrete, separate levels.
How is light like a wave? ♦ There are interference patterns. ♦ Light beams pass through each other.
What condition needs to be met in order for electrons to be emitted? Light must be yellow or white, with a high enough frequency.
What is Quantum? It is the minimum quantity of energy that can be lost or gained by an attom.
What happens when an excited atom returns to the ground state from an excited state? Light is released when the photon hits ground state.
How many ground states do the atoms of a given element have? 1 ground state
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