Number of protons: 28 and 28

Number of electrons: 28 and 26

Number of neutrons: 30 and 32

6.02 x 10²³  

You can remember this by thinking of mole day.  Mole day is celebrated at 6:02 pm on October the 23rd.  

Avogadro's number is the number of atoms in one mol (12 grams) of carbon-12.  It is also the number of atoms in 1 mol of any compound.

Protium - 1 proton, 1 neutron

Deuterium - 1 proton, 2 neutrons

Tritium - 1 proton, 3 neutrons

True or False:

Almost all elements exist as two or more isotopes, and these isotopes are present in the same proportions in any sample of a naturally occuring element.

(40)(0.60)+(44)(0.25)+(41)(0.15) = Q

Q = 41.15 g/mol

E=hf

h is plank's constant and f is the frequency of radiation.  Plank's constant will be provided on test day.  Remember, quanta are the energy bundles emitted as electromagnetic radiation from matter.

E = hc / λ

The energy of a photos equals plank's constant times the speed of light divided by the wavelength of the radiation.

True or False:

Each element can have its e- exicted to different distinct energy levels.  All elements possess the same atomic emissions spectrum.

False

Each element possesses a unique atomic emissions spectrum.  Atomic emissions spectroscopy is used to identify elements.  It is especially useful in the analysis of stars and planets.

The principle quantum number = n.  The larger n gets the higher the energy level and radius of the electron's orbital.  Each orbital shell can hold 2n² electrons.  The energy difference between n=3 and n=4 is less than it is between n=1 and n=2.  Remember. energy change is higher the closer you are to the nucleus.  As n increases, the orbital becomes larger and the electron spends more time farther from the nucleus. As n increases, the electron is also at a higher potential energy and is therefore less tightly bound to the nucleus.

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The azimuthal quantum number = L.  It tells you the shape and number of subshells within the principle level (n).  L can be any number zero and up to one less than the principle quantum number (n-1). 

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if l = 0 this is known as the S subshell (1 orbital)

if l = 1 this is known as the p subshell (3 orbitals)

if l = 2 this is the d subshell (5 orbitals)

if l =3 this is the f subshell (7 orbitals)

The maximum number of electrons that can exist in a given subshell is equal to 4L+2

The magnetic quantum number = M_l. It tells you which orbital in a subshell is most likely to contain an electron at any given time.  When l=0, M_l is limited to zero.  If L=1, M_l can be +1, 0, and -1.  If L=2, Ml can be -2, -1, 0, +1 and +2.  

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The spin quantum number is M_s.  Two possibilities exist, the spin can either be +1/2 or -1/2.  When two electrons are in the same orbital they must have opposite spins.

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Hund's rule states that within a given subshell, orbitals are filled such that tere are a maxiumum number of half filled orbitals with parallel spins.

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Unpaired electrons will orient their spins in alignment with the magnetic field and the material will have a weak attraction to the magnetic field.  

In such compounds atoms of these elements have some inner electron shells that are incomplete, causing their unpaired electrons to spin like tops and orbit like satellites, thus making the atoms a permanent magnet tending to align with and hence strengthen an applied magnetic field.

Paramagnetic materials have a small, positive susceptibility to magnetic fields. These materials are slightly attracted by a magnetic field and the material does not retain the magnetic properties when the external field is removed. Paramagnetic properties are due to the presence of some unpaired electrons, and from the realignment of the electron paths caused by the external magnetic field. Paramagnetic materials include magnesium, molybdenum, lithium, and tantalum.

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Diamagnetic materials have a weak, negative susceptibility to magnetic fields. Diamagnetic materials are slightly repelled by a magnetic field and the material does not retain the magnetic properties when the external field is removed. In diamagnetic materials all the electron are paired so there is no permanent net magnetic moment per atom. Diamagnetic properties arise from the realignment of the electron paths under the influence of an external magnetic field. Most elements in the periodic table, including copper, silver, and gold, are diamagnetic.

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Ferromagnetic materials have a large, positive susceptibility to an external magnetic field. They exhibit a strong attraction to magnetic fields and are able to retain their magnetic properties after the external field has been removed. Ferromagnetic materials have some unpaired electrons so their atoms have a net magnetic moment. They get their strong magnetic properties due to the presence of magnetic domains. In these domains, large numbers of atom's moments (10¹²to 10¹⁵) are aligned parallel so that the magnetic force within the domain is strong. When a ferromagnetic material is in the unmagnitized state, the domains are nearly randomly organized and the net magnetic field for the part as a whole is zero. When a magnetizing force is applied, the domains become aligned to produce a strong magnetic field within the part. Iron, nickel, and cobalt are examples of ferromagnetic materials. Components with these materials are commonly inspected using the magnetic particle method.

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Fe: 1s²2s²2p⁶3s²3p⁶4s²3d^{6 eight total}

Se: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p^{4 six total}

S: 1s²2s²2p⁶3s²3p^{4 six total}

Look at how many valence e- it has in total by looking at the group number.  Then identify the outtermost shells.