The Atom Review

The Atom

Review

Battle of the Greeks

• Aristotle: Continuous Theory

  -Matter can be divided infinitely

• Democritus & Leucippus: Discontinuous Theory

  - There is a tiny indivisible particle called an atom 

Dalton's Atomic Theory

1. Elements are made of atoms

2. Atoms of an element are the same.

3. Compounds are formed from combinations of atoms

JJ Thomson: Plum Pudding Model

Discovered the electrons while performing experiments with cathode rays

Ernest Rutherford: Nuclear Model

Performed Gold Foil Experiment

- Proved the atom was mostly empty space

- Discovered the dense, tiny, positive nucleus

Niel's Bohr: Planetary Model

• Proposed e^- traveled in fixed paths around the nucleus.  

• Each level can hold a maximum # of e^-

• Energy Level = Shell

Modern Atomic Model

• AKA Wave-Mechanical or Electron Cloud

• e^- behave like waves and particles

• Orbitals = most probable location of an e^-

• Electrons don't orbit the nucleus

Multiple Choice

What happened to the cathode ray during Thomson’s experiment?

• It was repelled by a positive charge

• It bounced back to the cathode

• It was stopped by a magnet

• It was deflected away from a negative charge

Multiple Choice

Which of the following was a result of the gold foil experiment?

• Most alpha particles bounced back.

• All alpha particles went straight through.

• Some alpha particles bounced back.

• None of the above

Multiple Choice

Number 1 is _ while number 2 is _.

• (+), (-)

• (-), (+)

• neutral , (+)

• neutral, (-)

Multiple Choice

What conclusion did Rutherford come to after the gold foil experiment?

• Most of the atom is empty space.

• A dense region of (+) charge existed in the atom.

• Thomson’s model was incorrect.

• All of the above

Excited vs Ground State

• Electrons jump to higher energy level when energy is absorbed

• Electrons return to original ground state energy level when energy is released as light

• Emission spectra used to identify elements (fingerprint)

• Number of electrons doesn't change

Multiple Choice

Which of the following shows an excited state electron configuration?

• 2-7-1

• 2-4

• 2-8-4

• 2-8-1

Multiple Choice

Which is a possible excited state electron configuration for Si?

• 2-8-4

• 1-9-4

• 2-8-8

• 2-8-3-1

Multiple Choice

The energy of an electron __________ as it moves further away from the nucleus

• increases
• decreases

Multiple Choice

What happens to energy as an atom goes from ground state to excited state?

• It increases

• It decreases

• It remains the same

Using the Periodic Table

• # p⁺ = 8

• # e^- = 8

• # n⁰ = 16 - 8 = 8

Multiple Choice

The nucleus of most atoms are made of:

• protons and electrons

• neutrons and electrons

• electrons and protons

• protons and neutrons

Multiple Select

The letter “X” in the diagram marks the:

select all that apply

• Location of the neutrons

• Electron cloud

• Nucleus

• Region of greatest density

• Location of the electrons

Multiple Select

Which of the following descriptions apply to the nucleus?

(select all that apply)

• positively charged

• mostly empty space

• small

• dense

Multiple Choice

The _ constitute most of the volume of an atom

• nucleus

• protons

• electrons

• neutrons

Isotopes

• Same number of protons & electrons (atomic #)

• Different number of neutrons (mass number)

Multiple Choice

If we assume pink represents protons and green represents neutrons, the nucleus depicted here is:

• boron-5

• boron-6

• boron-11

• carbon 11

Multiple Select

What is special about the atomic number?

• Equals the number of protons in an atom

• Identifies an element

• Equals the number of electrons in an atom

• Equals the number of neutrons in an atom

Multiple Choice

A carbon isotope consists of 6 protons, 6 electrons and 8 neutrons.  What is the mass number for this isotope?

• 12
• 14
• 6
• 8

Multiple Choice

A neutral atom of the isotope ²⁶₁₂Mg would consist of

• 12 protons, 26 neutrons, 26 electrons
• 26 protons, 12 neutrons, 26 electrons
• 26 protons, 14 neutrons, 14 electrons
• 12 protons, 14 neutrons, 12 electrons

Weighted Atomic Mass

• Atomic mass = average of naturally occurring isotopes

• Atomic mass will be closer to the most abundant isotope

Multiple Choice

A new element, Tyserium (Ty), has recently been discovered and consists of two isotopes. One isotope has a mass of 331 amu and is 35.0 % abundant. The other isotope is 337 amu and is 65.0 % abundant. What is the mass of Ty as it appears on the periodic table?

• 335 amu

• 334 amu

• 333 amu

• 332 amu

Fill in the Blank

Magnesium has three of its own isotopes. 78.7% is Magnesium-24. 10.13% is Magnesium-25. 11.17% is Magnesium-26. Calculate the relative atomic mass of Magnesium, to two decimal places.