AP Chem Unit 1

mole to atoms

6.022 × 10^ 23

Avogadro’s number

N_A

Unknown substances=

products

An isotope is

An atom of an element with different number of nuetrons

Mass spectrometer

Displays the spectrum of masses of molecules

• Chemical samples are ionized and passes through a magnetic force that measures the mass to charge ratio.

• A spectrum is then shown of different mass to charge ratios of the ions in the sample

Spectrometer

Measures mass to charge m/z

Average mass is calculated from the..

isotopes of an element weighted bby their realtive abundances

Relative abundance

The relative proportion of the various isotopes

Average atomic mass formula

(Rel. abundance isotope 1) x (mass isotope 1)…

Percent element

(# of atoms)(atomic mass)/(molar mass of mpnd) x 100%

Electron configuration is based

on the quantum mechanical model

n

describes distance from nucleus (principle quantum)

I

describes shape of orbital (angular quantum)

M1

describes orientation of orbital (magnetic quantum)

Ms

describes spin of electron (wave) (spin quantum)

orbital

probable location of finding an electron s orbital

Coulombs Law

The force between two charged particles is proportional to the product of the 2 charges, as well as the force is also inversely proportional to the squared radius between them.

Force equation

F=Ke q1q2/r²

Force decreases..

the further away the particles are

The higher charges and smaller distance between charge results in BLANK force of attraction.

Greater

It takes more energy to remove electrons that are..

closest to the nucleus

Aufbau Principle

Electrons are added to the lowest subshell first and build up

Hunds Rule

each subshell should have one electron housed in it before one is doubled up

Pauli Exclusion Principle

no 2 electrons can have the same set of 4 quantum numbers (spins have to be oppsiites)

Paramagnetic Aroms

has unpaired spins/electrons

Diamagnetic Atoms

Atoms with full orbital (all paired)

How do you find the shortcut electron configuration

find noble gas (gr 18) that is in the same row

Photoelectron Spectroscopy (PES)

An experimental technique that measures the relative energies of electrons in atoms or molecules. It ejects electrons from the material using high energy electromagnetic radiation.

What do the PES graphs show you

the relative number of electrons and their corresponding bonding energy (the amount of energy needed to remove an electron from an atom)

The electrons with the highest binding energy are..

the ones that have the greatest coulombic attraction to the nucleus because they are closest to the nucleus.

Energy equation

E=hv(frequency)

Binding energy equation

Binding energy= KE electron

Energy photon equation

E photon= B.E + KE electron

Underlying principles of photoelectron spectroscpy-The shell model

energy of the electron suggests an energy arrangement of electrons of shells (bohr’s planetary model)

Underlying principles of photoelectron spectroscpy-Ionization energy

is the energy to remove an electron from an atom (endothermic) and makes a cation

Underlying principles of photoelectron spectroscopy-Coulombic force of attraction

is a force of attraction between positive and negative charges. for the atoms this is the attraction of the electrons in the shell for the protons in the nucleus.

Underlying principles of photoelectron spectroscopy-Shielding

is a force that can create less attraction of an outer electron to the proton in the nucleus because of other electrons closer to the nucleus (repelling)

Inner core electrons

in the inner shells

valence electrons

only on outer shell

First ionization energy

the minimum amount of energy that is required to remove the outermost, least tightly held, electron from an atom in the gas phase.

Force attraction equation

F= k q1q2/d2 (q=magnitude of charge association w/ a particles) (d=distance between charged particles)

the greater the distance between the electrons and the protons in the nuclues, the BLANK force of attraction

Lower

The closer to things are in space, the BLANK the force of attraction between these objects exist

Greater

Closer + oppositely charged =

greater force of attraction

Coulombic attraction

the electrostatic attraction between two charged particles (nuclues/total protons/neg. charged electrons)

Coulombs Law

the attraction between two charged particles is proportional to the magnitude of the charge ad inversely proportional to the distance between them

The larger the charge..

the more attractive forces between particles

The effective nuclear charge

the net positive charge experienced by valence electrons-can be approximated by Zeff=Z(atomic number)-S(inner electron)

Atomic Radius

A measure of the size of its atoms

Bonding atomic radius

1/2 d (distance between covalently bonded nuclei)

(Radius Left to right) Increasing the number of protons gives a …

higher effective nuclear charge/stronger force of attraction pulling the electrons close to the nucleus, making a smaller radius

(Radius)According to coulomb’s law the increase in positive charge..

increases the force of attraction experienced by each electron, thereby decreasing the radius

According to coulomb’s law the force of attraction BLANK as the distance between the electrons and protons increases.

Decreases

Radius down (top to bottom)

• Valence electrons have more energy and are further from nucleus

• The outer electrons experience a greater shielding effect and a decreases effective nuclear charge

• New shells are added with larger orbitals (the principal quantum number increases)

Ionic size depends on…

Nuclear charge, number of electrons, and the orbitals in which the electrons reside

Cations are BLANK than their parent atom

Smaller

Anions are BLANK that their paren atom

Larger

Ionic Radius left to right

• The radii of cations decrease

• When you encounter the first anion, the radius dramatically increases, then radii continues to decrease

(Ionic radius) According to coulomb’s law the increase in positive charge..

increases the force of attraction experienced by each electron, thereby decreasing the radius.

Isoelectronic species

Share the same electron configurations but have different radii, bc different amount of protons in nucleus

As the ratio of protons to electrons increases…

the forces of attraction on those electrons increase

Ionic size BLANK with an increasing nuclear charge

Decreases

Cations are always BLANK than anions

Smaller

First ionization energy

amount of energy required to remove an electron from the ground state of a gaseous atom or ion. (remove first electron)

It requires BLANK energy to remove each succesive electron

More

Metals have a BLANK ionization energy than nonmetals

lower

Z_eff increases

Left to right

(Ionization energy) As you go across a group coulbs ’s force of attraction BLANK

increase

(Ionization energy) As you go down a group BLANk energy is required as you go down

Less

Electron affinity

energy release when an electron is added to a gaseous atom

Nonmetals have BLANK electron affinity bc of their atomic structure

Greater

Electronegativity

A measure of the ability of an atom in a chemical compound to attract electrons

Electronegativity down trend

Decreases down a column as there’s a greater distance from the nucleus and bc more electron shielding

Electronegativity left to right trend

Increases left to right because atomic radius decreases while number of protons in effective nuclear charge is increasing. So it increases as atomic radius decreases bc when two atoms are involved in a chemical bond, the valence electrons will experience a greater attraction for the positive nucleus that is closest to them.

Ionic bonds form when

electrons are transferred

Covalent bonds form when

electrons are shared

The greater the difference between the atoms involved in the bond..

the more ionic character in the bond

In order to maintain nuetrality

The number of electrons that are transferred must equal the number of electrons gained(bc its based on electron configuration)

Elements in the same group will form the same

metal/nonmetal analogous compounds

Metals

• Tend to form cations

• Lustrous

• Malleable

• Ductile

• Good conductors of heat/electricity

• lose electrons to gain electron configurations that are isoelectronic with the noble gas configurations

• Metal oxides tend to be basic

Metalloids have

characteristics of metals and nonmetals

Nonmetals

• tends to form anions

• dull/brittle

• poor conductors of heat/ electricity

• gain electrons in reactions with metal to aquire noble gas configurations

• Most nonmetal oxides are acid

Group 1

Alkali metals

Group 2

Alkaline earth metals

Group 16

Chalcogens

Group 18

Noble gases (rare gases)

Law of definite proportions

the ratio of masses in a compound must always be the same

More protons =

greater binding energy