Exam 2: Ch. 4 (CHEM 1305)

the size of ping pong balls

4.1: If a baseball were the size of the Earth, about how large would its atoms be?

physical models represent the object at a more convenient scale, conceptual models are a representation of how the system behaves

4.1: what is the difference between a physical model and a conceptual model?

the charge of an electron, 1.60 x 10^19 and found the mass of electrons to be less than hydrogen, the smallest atom

4.2: What did Millikan discover about the electron?

Because the like charges repel each other

4.2: Why is a cathode ray deflected by a nearby charge or magnet?

the angle of deflection is proportional to the ratio of the particle's charge to its mass

4.2: what did Thomson discover about the electron?

they were deflected by the atomic nucleus

4.3: To Rutherford's surprise, what was the fate of a tiny fraction of alpha particles in the gold foil experiment?

used the gold foil experiment to show the atom was mostly empty space and discovered the atomic nucleus

4.3: What did Rutherford discover about the atom?

the electrons of different atoms repel each other

4.3: What kind of force that prevents atoms from squishing into one another?

mass number is the total number of protons and neutrons, atomic number is only protons

4.4: Distinguish between atomic number and mass number.

atomic mass is the sum of all of the nuclear components (nucleus plus electrons), mass number is protons plus neutrons

4.4: distinguish between mass number and atomic mass.

the number of protons in an element

4.4:What role does atomic number play in the periodic table?

small

4.5: Does visible light constitute a large or small portion of the electromagnetic spectrum?

separates the light into its different frequencies

4.5: What does a spectroscope do to the light coming from an atom?

the oscillation of electrons generate electromagnetic radiation

4.6: What causes an atom to emit light?

light energy is quantized similarly to matter (light energy consists of some number of fundamental units)

4.6: What was Planck's quantum hypothesis?

No

4.6: did Bohr think of his planetary model as an accurate representation of what an atom looks like?

because you can identify the elements in a light source from them

4.6: why do we say atomic spectra are like fingerprints of elements?

2

4.7: how many electrons can reside in a single atomic orbital?

Louis de Broglie

4.7: who first proposed that electrons exhibit the properties of a wave?

valence

4.8: which electrons are most responsible for the properties of an atom?

Spectroscope

A device that uses a prism or diffraction grating to separate light into its color components and measure their frequencies.

Noble gas shell

A graphic representation of a collection of orbitals of comparable energy in a multi electron atom. A noble gas shell can also be viewed as a region of space about the atomic nucleus within which electrons may reside.

Probability cloud

A plot of the positions of an electron of a given energy over time as a series of tiny dots.

Proton

A positively charged subatomic particle found in the atomic nucleus.

Conceptual model

A representation of a system that helps us predict how the system behaves.

Physical model

A representation of an object on some convenient scale.

Energy-level diagram

A schematic drawing used to arrange atomic orbitals in order of increasing energy levels.

Quantum

A small, discrete packet of energy.

Atomic orbital

A volume of space where an electron is likely to be found 90 percent of the time.

Neutron

An electrically neutral particle found in the atomic nucleus.

Electron

An extremely small, negatively charged subatomic particle found outside the atomic nucleus.

Quantum number

An integer that specifies the quantized energy level within an atom.

Isotope

Any member of a set of atoms of the same element whose nuclei contain the same number of protons but different numbers of neutrons.

Nucleon

Any subatomic particle found in an atomic nucleus. Another name for either proton or neutron.

Ionization energy

The amount of energy needed to pull an electron away from an atom.

Electron configuration

The arrangement of an atom's electrons within orbitals.

Electromagnetic spectrum

The complete range of waves, from radio waves to gamma rays.

Atomic nucleus

The dense, positively charged center of every atom.

Effective nuclear charge

The nuclear charge experienced by outer-shell electrons, diminished by the shielding effect of inner-shell electrons and also by the distance from the nucleus.

Mass number

The number of nucleons (protons plus neutrons) in the atomic nucleus. Used primarily to identify isotopes.

Atomic number

The number of protons in the atomic nucleus of each atom of a given element.

Atomic spectrum

The pattern of frequencies of electromagnetic radiation emitted by the energized atoms of an element, considered to be an element's "fingerprint."

Inner-shell shielding

The tendency of inner-shell electrons to partially shield outer-shell electrons from the attractive pull exerted by the positively charged nucleus.

Atomic mass

The total mass of an atom. The atomic mass of each element presented in the periodic table is the weighted average atomic mass of the various isotopes of that element occurring in nature.