Atomic Models and Properties of Atoms

Bohr's model uses the following concepts

- electrons exist in circular orbits (the electrostatic force between the positive nucleus and the negative charge on the electrons, rather than on gravitational pull) - Electrons can exist only in a series of allowed orbits, also described as energy levels, which means that the energy of electrons in atoms is quantized - While the electron remains in orbit; it does not radiate energy - Electrons jump between orbits by absorbing or emitting photons carrying an amount of energy quell to the difference in the energy levels of the electrons

Quantum Mechanical model of the Atom

An atomic model in which electrons are treated as having wave characteristics

Electron configuration

An atoms EC shows the number and arrangement of electrons in its orbitals.

Element with the Largest Atomic Radius

Cesium

Element with the Lowest Ionization Energy

Cesium

Group with Highest Electron Affinity

Group 17 (halogens) and to a lesser degree Group 16. (reactive nonmetals) these atoms have high ionization energies and high electron affinities. As a result it takes a great deal of energy to remove electrons from these atoms, however, these atoms attract electrons strongly, and form negative ions in ionic compounds.

s-block elements

Groups 1 and 2. The s orbital can hold a total of 2 electrons, therefore s block elements span two groups

p-block elements

Groups 13-18, Five d orbitals can hold 10 electrons

Element with Smallest Atomic Radius

Helium

Element with the Highest Ionization Energy

Helium

f-block elements

Includes the inner transition elements. Many exceptions make predictions difficult. Because there are 7 f orbitals, with a max of 14 electrons, the f block spans 14 groups.

Quantum Numbers

Integers arising from the solutions to the wave equation that describe specific properties of electrons in atoms specify the properties of atomic orbitals and the properties of electrons in orbitals

MRI

Magnetic Resonance Imaging technology uses radio waves along with a powerful magnet and a computer to generate images of soft tissue. Like electrons, protons spin on their axes. However, the orientation of these axes is random. The strong magnetic field generated by the MRI magnet affects the protons in hydrogen atoms in body tissue, causing their axes to align with the same orientation. (like a compass) When exposed to radio waves at a specific frequency, certain protons are momentarily 'knocked' out of this alignment. When the radio signal is removed, these protons re-align with the magnetic field, emitting their own radio waves as they do so.

Electron Configuration (specific def.)

Patterned order by which electrons fill subshells and energy levels in an atom. First number designates principal quantum number (n); s, p, d, f, or g specify the subshell (l); and the superscript indicates the number of electrons in that subshell.

Aufbau Principle

States that each electron occupies the lowest energy orbital available. A principle behind an imaginary process of building up the electronic structure of the atoms, in order of atomic number

Electron Affinity

The energy change that accompanies the addition of an electron to an atom in the gaseous state

7 Tesla - Canadian Research in Action

The world's most powerful MRI and the only one of its kind in Canada focused on Epilepsy Research. Dr. Jorge Burneo, from the University of Western Ontario in London, and his team are using a technique called magnetic resonance spectroscopy (MRS) to investigate metabolic changes in regions of the brain where seizures are generated.

d-block elements

Transition metals as well as group 12 of the main group of elements. The d block spans ten groups, having the ability to carry 10 electrons in its orbitals

Orbital diagram

Uses a box for each orbital in any given principal level. An empty box represents a box with no electrons. A box that has a single arrow represents a half filled orbital.

Atomic Orbital

a mathematical expression describing the probability of finding an electron at various locations; usually represented by the region of space around the nucleus where there is a high probability of finding an electron. This region in space is related to a specific wave function.

Atomic Radius

half the distance between the nuclei of two adjacent atoms; for metals, between atoms in a crystal, and for molecules, between atoms chemically bonded together.

magnetic quantum number, m(l)

indicates the orientation of the orbital in the space around the nucleus. The value of m(l) depends directly on the value of l if l is 0, m(l) is 0 if l is 1, m(l) is -1,0,1 if l is 2, m(l) is -2,-1,0,1,2 if l is 3, m(l) is -3,-2,-1,0,1,2,3

Orbital Shape quantum number, l

it describes the orbital shape. It refers to energy sub levels, or sub-shells within each principal energy level Each value of l is identified by a specific letter- s,p,d,f l=0 ; orbital has the letter s (circle, sphere) l=1 ; orbital has the letter p (half a 4 leaf clover) l=2 ; orbital has the letter d (4 leaf clover) (n=3, l=2 it is half a clover on the z plane and a circle on the x-y plane) l=3 ; orbital has the letter f (not covered in this course)

Bohr's Model

proposed that electrons move in definite orbits around the nucleus, much like planets circling the Sun. These orbits are located at specific distances from the nucleus; have certain energy levels (the more energy it has the farther the orbit is from the nucleus) Niels Bohr ( 1885-1962) He was able to calculate the energy and radii of the allowed orbits for the hydrogen atom

Max Born

showed that the wave functions could be used to determine the probability of finding the electron at any point within the region of space described by the wave function

The spin quantum number, m(s)

specifies the direction in which the axis of the electron is oriented and has only two possible values: +1/2 and -1/2

The principal Quantum Number, n

specifies the energy level, or shell, of an atomic orbital and its relative size

Pauli exclusion principle

states that a maximum of two electrons may occupy a single atomic orbital, but only if the electrons have opposite spins

Hund's Rule

states that the lowest energy state of an atom has the maximum number of unpaired electrons allowed by the Pauli exclusion principle in a given energy sub level in other words, single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can occupy the same orbitals.

Ionization Energy

the energy needed to completely remove one electron from a ground-state gaseous state