The quantum model of atom and periodicity-chapter 3

light

Form of energy that can be described as a moving wave of magnetic and electrical potential

Visible light.

Light that can be perceived by human eye

Wavelength

Distance between a corresponding points

Frequency

No of crests that pass a given point per second

electromagnetic spectrum

All of the frequencies or wavelengths of electromagnetic radiation

Wavelength correlation to frequency

Longer wavelengths - low frequency, shorter wavelengths - higher frequency

Photo electric effect

electrons are ejected when light shines on a metal

Conditions for photo electric effect

1- light must be of a minimum specific energy
2-shining light of higher energy doesn't increase e-
3-brightness of the light is proportional tothe number of electrons emitted

Electrons emitted from the photoelectric effect are called?

Photo electrons

Einstein's explanation of the photoelectric effect

a photon with at least the minimum energy that strikes an electron will cause that electron to be ejected from the atom

dual nature of light

the statement that light exhibits both wave and particulate properties

wave-particle duality

the concept that all matter and energy exhibit both wave-like and particle-like properties

What are particles of light called?

photons

Work function

Minimum energy required to remove an election from the surface of the material in a vacuum

What is work function related to?

Threshold frequency

What is threshold frequency

Minimum frequency of light that can eject electrons

Kinetic energy and work function.

When photon impacting the surface of the metal has energy above threshold energy5 the excess energy of the photon his transferred to the electron in the form of kinetic energy

Light absorption

occurs when an atom absorbs light energy from the surroundings and gains energy

light emission

An atom has excess energy and gives of energy by emitting light

absorption spectrum

The range of a pigment's ability to absorb various wavelengths of light.

Where are elections found according to Neils Bohr

Found at specific distances from the nucleus in orbits.

What are the circular paths that electrons travel in called?

Discrete energy levels.

Is Bohr's model accurate?

No - electrons do not travel in circular orbits

What does bohr's theory explain?

The absorption spectra

What is the lowest energy level called ( closest to the nucleus)

Ground state

When is absorption spectrum observed?

When e- absorb energy and move to higher levels - call excited states

What does the energy of light absorbed equal?

The difference between the existing energy levels in the atom.

Individual lines in emission spectrum

Line spectrum

Biggest energy difference in any atoms energy levels

First and second energy levels

What happens to energy levels as we get further away from the nucleus?

The further we get the closer the energy shells get to each other.

An electron removed from anatom has - energy f level?and energy value?

Energy level - infinity and energy value - o J

Lower energy levels are

Given negative values because,they must have less energy than an electron in the highest energy level.

Schrödinger wave equation

Gives probable position of an electron in an atom

How many subshells in s,p,d,f

S-1
P-3
D-5
F-7

No of orbitals, max no of e- per orbital and max no of e- in sub shell in s

1,2,2

No of orbitals, max no of e- per orbital and max no of e- in sub shell in p

3,2,6

No of orbitals, max no of e- per orbital and max no of e- in sub shell in d

5,2,10

No of orbitals, max no of e- per orbital and max no of e- in sub shell in f

7,2,14

What are the 4 quantum numbers

n- principle quantum number
l- angular momentum quantum
ml- magnetic quantum number
ms- spin quantum number

Principle quantum number indicates(n) _____?

Identifies the principle quantum number, the principle energy level or shell of the electron

Can values of principal quantum number be negative

No only positive starting with 1 {n=1,2,3}

angular momentum quantum number l

Identifies sub shell of electron

How is angular momentum quantum number l related to principle quantum number n

Allowed number of values depend on n l=0 to l= (n-1) for a shell

Value of l for different subshells

s- 0
p-1
d-2
f-3

magnetic quantum number (ml)

Identifies the orbital that the electron occupies

How is magnetic quantum number (ml) related to angular quantum number (l)

ml = -l to +l

Spin quantum number (ms)

-tells you the spin of the e-
- values are ±1/2

Pauli Exclusion Principle

no two electrons in the same atom can have the same set of four quantum numbers

s orbital shape

spherical

p orbital shape

dumbbell - ( 3 p orbitals, each of which has 2 3D lobes )

d orbital shape

4 leaf clover

f orbital shape

flower

Subshell lowest to highest energy

s < p < d < f

Orbital diagrams

a pictorial way of showing electronic structure of an atom

How is an orbital represented

By a short horizontal line

degenerate

Orbitals within a subshell are at the same energy level

How are electrons represented inorbital diagrams

Arrows

. What is the spin when an orbital holds 2 electrons

Opposite spin

What is the spin when a subshell holds morethanoneunpaired election

Same spin

Are electrons shown in highest or lowest energy levels

In lowest possible energy levels -groundstate

What isgroundstate?

Ground state is the most stable state

Aufbau Principle

the rule that electrons occupy the orbitals of lowest energy first

Hund's Rule

Electrons within agiven subshell remain as unpaired as possible

What affects the magnetic properties of a substance

Presence or absence of unpaired elections

paramagnetic

A substance with atleastone unpaired electron_-and is attracted to a magnetic field.

diamagnetic

A substance with no unpaired elections__- weakly repelled from a magnetic field

Electron configurations

the arrangement of electrons in an atom

Specific notation for electron configuration

1. list each sub shell in order of
2.add superscript toe each sub-shell to indicate-how many
electrons it contains
3.the sum of the subscripts equals the total number of electrons in the atom or ion

Electronic configuration related to groups

Each group have the same outermost configuration

Outermost electronic configuration for alkali metals ( group 1)

ns1

Outermost electronic configuration for alkaline earth metals ( group 2)

ns2

Outermost electronic configuration for halogens (group 17)

ns2np5

What do valence electrons determine?

the chemical properties of an element

abbreviated electron configuration

[noble gas] then the rest of configuration

anomalous electron configurations

Cr and Cu

Electron configuration of ions

No of electrons is- atomic number +

+ charge for -ve ions
- charge for +ve ions

Isoelectrons

same electron configuration for ions and atoms

Electron configuration of transition metal ions

Metal atoms form ions by losing energy levels
Transition metals lose electron sublevel

What do valence electrons display

Periodicity

Periodicity in group (IA) and in group 2A

1A - 1 e-in their outer s orbital
2A - 2 e- in their outer s orbital

core electrons

all electrons that are not valence electrons

Where are valence electrons in main group elements

In the biggest occupied energy level.

How are valence electrons related to chemical properties

Valence electrons are involved in bonding, so elements with the same valence electron configuration

Size of atoms and ions is determined by

Their electronic structures and the interactions between the oppositely charged nucleus and electrons

Where do electrons lie and what's the charge,

Outside the nucleus, -1

Where do protons lie and what's the charge

Within the nucleus, +1

Electrostatic principles

The interactions between the electrons and the nucleus
It states
1.Oppositely charged particles attract each other.
2.Like-charged particles repel each other.
3.As the charges increase, so does the attraction or repulsion.
4.As the two charged bodies get closer to each other, the force of attraction or repulsion gets stronger.

effective nuclear charge (Zeff)

The net positive charge from the nucleus that an electron experiences

Valence electrons in relation to zeff

Zeff is lower that the actual nuclear charge, zeff <z

Some nuclear charge is shielded by core electrons

Zeff= z- s

shielding and nuclear charge

Each valence electron shields the other to a small extent, but core electrons anemone effective at shieldingthan valence electrons

Slater's rule is used to calculate the value of Shielding

Additional valence electron contribute to a value of 0.35 toward the shielding
Comes electrons contribute a value of 0.85 towards the shielding

General trends in Z eff

1. Z eff increases across a row of the period table
2. Z eff decreases slightly going down a group

atomic radius trend

decreases across a period and increases down a group

Why does atomic radius decrease across a period?

1. The nuclei of atoms become more and more strongly positive while the number of core electrons remains the same, causing Z eff to increase
2. Valence electrons experiencing higher Z eff pulled more tightly to the nucleus making the atomic radius smaller

Ionic Radius: Cations

Positive charge, lost electrons, gets smaller

Ionic Radius: anions

Negative charge, gained electrons, gets bigger

Ionization Energy (IE)

the energy required to remove one electron from a neutral atom of an element

What factors affect ionization energy?

Atomic radius and zeff

Atoms get larger - smaller zeff - IE?

IE decreases, making it easier to remove an electron