AP Chemistry: UNIT 1 ATOMIC STRUCTURES AND PROPERTIES

7~9% of the exam

Frequency

number of waves that pass by in a given amount of time

Relationship between wavelength and frequency?

Inversely proportional

“Quanta”

Discrete packets of energy

Equations relevant to wave calculations

Higher frequency =

Higher KE (using ultraviolent light instead of yellow visible light)

Electrons can only be located in very specific _______________ around the nucleus

energy levels

Electrons cannot exist in _____________ energy levels

BETWEEN

Heisenberg’s Uncertainty Principle

Can never be certain about an electron’s location and momentum simultaneously

Explain what causes green light vs. red light to be emitted according to Bohr’s model

What do the dots in the electron cloud model represent

likelihood of finding electrons in surrounding parameter/at any given spot

s orbitals appear as…

spheres

p orbitals look like…

3 dumbbells stacked together

Electron Configuration

Aufbau principle

In the ground state of an atom or ion, electrons fill subshells of the lowest available energy level first

Pauli’s Exclusion Principle

IN a given atom, no two electrons can occupy the same orbital WITH the same spin

Hund’s rule

the lowest energy configuration for an atom is the one having a maximum number of unpaired electrons

• For orbitals of same energy, add one electron per orbital before pairing

FORMAT FOR ELECTRON CONFIGURATIONS

Electron configuration of ions

figure out if the ion has lost or gained electrons
+ charge = LOST electrons

- charge = GAINED electrons

Isoelectronic

Two ions have the same number of electrons, therefore the same electron configuration

Why do some electron configurations no follow the normal pattern due to stability reasons?

ONLY occurs in large atoms, DUE TO CLOSE PROXIMITY OF SUBSHELLS, electrons move to increase stability

MOVE FROM S

Stability of all orbital types

Completely filled orbital- most stable

Half filled- less stable

Partially filled- least stable

ORDER OF FAVORABLE ELECTRON CONFIG.

Paramagnetic

Attracted by a magnet because of unpaired electrons

Diamagnetic

Slightly repelled by magnets because all electrons are paired

Coulomb’s Law

IONIZATION ENERGY IS

FORCE OF ELECTROSTATIC ATTRACTION

Ionization energy

the amount of energy required to remove an electron from an atom

IE₁

1st ionization energy

Red spaces on IE graph

Ionization energy of core electrons; MUCH harder to remove from an atom

What do the peaks in a PES graph represent?

Number of electrons

On PES graph, what does a BE closer to y axis mean? (use normal legend)

greater nuclear charge/sometimes more electrons

BIGGER GAPS IN PES GRAPH

greater electron repulsions

Shielding

Electrons closer to the nucleus “shield” some of the positive charge of the nucleus from the electrons further from the nucleus

Core electrons

all electrons inside valence shell

ZEFF

Effective nuclear charge = the effect of the nuclear charge on a specific electron

Nuclear Charge

Charge of nucleus

Zeff calculations

Atomic Size Trend AND explanation

Why are anions bigger than parent

More electron repulsions, valence electrons are tightly held by the nucleus causing the ion to increase in size

Size trend for isoelectronic ions

All have the same electron configuration, and therefore the same number of energy levels

LARGER AMOUNTS OF + CHARGE FROM THE NUCLEUS = LARGER COULOMBIC ATTRACTIVE FORCE, MAKING THE ION SMALLER

IE trend

Be to B (IE)

AN electron gets added to the 2p orbital in B. This electron is slightly shielded by the 2s orbital making it easier to remove

N to O (IE)

O’s electron configuration ends in 2p⁴ There is repulsion between the paired electrons of the 2p orbital. This repulsion makes it easier to remove an electron

When does energy do a huge jump?

When all valence electrons have been removed

The first electron(s)______________ are from the _______ principal energy level

removed, HIGHEST

EA (Electron Affinity) trend

Electron affinity releases more energy as you go left to right

EXCEPTION: Noble Gases have a positive EA because it would require energy for them to gain an electron since this process is making the noble gas less stable, N ALSO HAS A + FOR SAME REASON

Electronegativity

Ability of an atom in a molecule to attract electrons to itself

Electronegativity trends

High electronegativity

High ionization energy, high negative electron affinity

Electron affinity

Energy change accompanying the addition of an electron

PROPOERTIES OF METAL

lustrous, malleable, ductile, good conductors of heat and electricity, form cations due to low ionization energy

NONMENTAL properties

dull, brittle, poor conductors of heat and electricity, can be solid, liquid, gas at room temp., form anions due to their large exothermic Electron Affinity

Metalloids

some characteristics of metals some of nonmetals, are semiconductors

Electrical Conductor how does it work

Electricity is the flow of electrons

-towards positive charge

-away from negative charge

IN CONDUCTORS, electrons will move away from their atom, conducting electricity

Insulators

do not allow electrons to flow because electrons that get excited REMAIN IN THEIR ATOMS

In conductors, electrons……

will move away from their atom and flow towards a positive charge thus conducting electricity

Metals form ____________ because they have __________, meaning its easy for them to lose electrons

cation, low ionization energy

Nonmetals have _____________ values meaning they will ___________________ to increase stability

larger exothermic electron affinity values, gain electrons

Metal reactivity trend

Nonmetal reactivity

Allotrope

existence of an element in two or more forms, which may differ in arrangement of atoms in crystalline solids

Why is IE of noble gases so high?

Atom form is so stable due to filled valence, largest effective nuclear charge = high IE, OVERALL UNREACTIVE

Spectroscopy

study of matter interacting with light

3 parts:

SOURCE OF LIGHT

SAMPLE OF MATTER
A DETECTOR

Spectrophotometry

Quantitative measure of transmitted or absorbed light, Specific to visible light and some areas of UV and IR

Mass Spec. can be used to separate…

atoms, isotopes, fragments of molecules BASED ON MASS

5 postulates of Dalton’s Atomic Theory

1) elements are made of extremely small particles called atoms

2)atoms of a given element are identical in size, mass, and other properties. Atoms of different elements DO differ in those 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

Isotopes

atoms of the same element with different mass due to differing number of neutrons