Atomic Structure, Spectra, and Quantum Mechanics in Chemistry

Atomic Number

Number of Protons (I.D. of the Atom)-----Also # of Electrons in an uncharged atom.

Mass Number

Number of Protons AND Neutrons.

Isotopes

Atoms with different numbers of neutrons.

Sodium-23

The M.C.I (most common isotope).

Sodium-22

An isotope of Sodium with a different mass number.

Ions

*no charge written if neutral (protons and electrons equal each other).

Anion

Formed by gaining electron(s) ---> negative.

Cation

Formed by losing electron(s) ---> positive.

Number of Neutrons

Mass # - Atomic #.

Planck's Equation

E = hf, where E is energy, h is Planck's constant, and f is frequency.

Planck's Constant

6.626 x 10^-34 J s.

Energy

Expressed in joules or kilojoules.

1 kJ

1 x 10^3 J.

1 cal

4.184 J.

1 J

Equivalent to a 10 watt light bulb for 1/10 of a second.

180 Calorie glass of soda

Equivalent to 180,000 cal.

Energy of green light

What is the energy of green light that has a wavelength of 550nm?

Kinetic Energy (KE)

Energy possessed by an object due to its motion.

Potential Energy (PE)

Energy possessed by an object due to its position or state.

Chemical Potential Energy

Energy stored in the bonds of chemical compounds.

180,000 cal = 753,120 J

This is the energy conversion for the soda.

Time to light bulb

75,312 sec to light a 10 watt bulb with energy from the soda.

Atomic spectra

Consist of discrete lines given off at specific wavelengths.

White light

Can be broken down into its color components by a prism or diffraction grating.

Sodium flame test

Has two distinct lines at 589.0 nm and 589.6 nm.

Qualitative TEST

Certain elements give off particular wavelengths of light.

Exciting electrons

Involves moving electrons from one energy level to another, which is quantized.

Ground state

The lowest energy state of an electron in an atom.

Copper flame

Produces a blue/green color.

Lithium flame

Produces a red color.

Rydberg Constant (RH)

2.180 x 10^-18 Joules (J).

Planck's constant (h)

6.626 x 10^-34 J s.

Bohr's model

Great for the hydrogen atom, but has limitations for more complex atoms.

Heisenberg's Uncertainty Principle

It is impossible to define the precise position of an electron in an atom at a given instant.

Quantum Mechanical Model of the Atom

Also known as the Electron Cloud Model, where electrons occupy orbitals.

Orbitals

3D areas where electrons have the highest probability of existing.

Balmer Series

A series of spectral lines of hydrogen.

Energy levels (n)

Quantized states that electrons can occupy, such as n=1, n=2, n=3, etc.

Spectral lines

Result from electrons dropping back down to ground state and releasing absorbed energy.

Diffraction grating

Used to see atomic line spectra.

Flame Tests

Laboratory tests to identify elements based on the color of flame produced.

Louis deBroglie

Proposed that if light can behave as particles and waves, then electrons can too.

Error in Bohr's equation for Helium

Calculating energies results in a 5% error, compared to 0.1% for Hydrogen.