Chapter 2 - Atoms and Elements Flashcards
Which machine can you use to pass a sharp metal tip over a flat metal surface, which allows you to scans the surface on an atomic scale? (Essentially taking pictures of atoms on the surface)
Scanning Tunneling Microscope (STM)
Other than taking pictures of atoms on the surface, what does the STM allow you to do?
It allows you to move individual atoms across the surface
- Total mass of the material you have before the reaction must equal the total mass of material you have at the end
- total mass of reactants = total mass of products
Law of Conservation of Mass
All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements
• Law of Definite Proportions
If a 10.0g sample of calcite contains 4.0g of calcium, how much calcite contains 0.24g of calcium?
0.60g of calcite
When 2 elements form 2 different compounds, the masses of B that combine with 1g of A can be expressed as a ratio of small, while numbers
Law of Multiple Proportions
Carbon combines with oxygen to form two different compounds. Carbon monoxide contains 1.33g of oxygen for every 1.00g of carbon. Carbon dioxide contains 2.67 g of oxygen for every 1.00g of carbon. What would the oxygen mass ratio be?
It would always be 2 since carbon dioxide is twice as big as carbon dioxide
2.67g / 1.33g = 2
- Each Element is composed of tiny, indestructible atoms
- All atoms of a given element have the same mass and properties
- Atoms combine in simple, whole-number ratios to form molecules of compounds
- In a chemical reaction, atoms of one element cannot change into atoms of another element (they simple rearrange the way they are attached)
Dalton’s Atomic Theory
Is the statement correct ACCORDING TO DALTONS THEORY:
1) Copper atoms can combine with zinc atoms to make gold.
2) Water is composed of many identical molecules that have one oxygen atom and two hydrogen atoms.
1) Incorrect. According to Dalton, atoms of an element cannot turn into atoms of another element by chemical reaction.
2) Correct. According to Dalton, atoms combine together in compounds in small whole number ratios.
Opposite charges _____
Ex: - and +
Attract
Like charges _____
• Ex: + and +
Repel
To be neutral, something must have no charge or ____
Equal amounts of opposite charges
A glass tube containing metal electrodes from which almost all the air has been evacuated
Cathode Ray Tube
What were the results of the J.J. Thomson’s Cathode Ray Tube Experiment?
- Cathode rays are made of tiny particles that have a negative charge (beam deflected towards the + plate)
- The amount of deflection was related to the charge and the mass of the particles
- Atoms are Not unbreakable
Cathode Ray particles became known as _____
Electrons
Tiny negatively charged particles found in all atoms
Electrons
What part of an atom was missing in Thomson’s Plum Pudding Atom?
The positively charged Protons
Certain elements constantly emit small, energetic particles and rays, which could penetrate matter
Radioactivity
Ernest Rutherford discovered that there were 3 different kinds of emissions:
Alpha (a) rays, beta (b) rays, and gamma (g) rays
Made of particles with a mass 4x H atom and + charge
Alpha (a) rays
Made of particles with a mass 1/2000th H atom and - charge
Beta (b) rays
Energy rays, not particles
Gamma (g) rays
What were Rutherfords Conclusions after his Gold Foil experiment?
- Atoms are mostly empty space, since most particles went straight through
- Atoms contain dense particles that are small in volume but large in mass, since a few particles bounced back
- The dense particle is positively charged, since some particles experienced large deflections
The ____ had essentially the entire mass of the atom
Nucleus
The nucleus is _____ charged
Positively charged
For an atom to be neutral, there must be equal number of _____ and ____
Protons and Electrons
The neutrally charged particle found in the nucleus alongside the proton is called the ____
Neutron
The number of protons and in the nucleus is called the ___
Atomic number
The Elements are arranged on the Periodic Table in order of their ____
Atomic numbers
Soddy discovered that the same element could have atoms with ____ ____, which he called isotopes.
Different masses