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block
A block of the periodic table of elements is a set of adjacent groups. The term appears to have been first used by Charles Janet. The respective highest-energy electrons in each element in a block belong to the same atomic orbital type. Each block is named after its characteristic orbital; thus, the blocks are:
s-block
p-block
d-block
f-block
g-block (hypothetical)
The block names (s, p, d, f and g) are derived from the spectroscopic notation for the associated atomic orbitals: sharp, principal, diffuse and fundamental, and then g which follows f in the alphabet.
The following is the order for filling the "subshell" orbitals, according to the Aufbau principle, which also gives the linear order of the "blocks" (as atomic number increases) in the periodic table:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, ...
For discussion of the nature of why the energies of the blocks naturally appear in this order in complex atoms, see atomic orbital and electron configuration.
The "periodic" nature of the filling of orbitals, as well as emergence of the s, p, d and f "blocks" is more obvious, if this order of filling is given in matrix form, with increasing principal quantum numbers starting the new rows ("periods") in the matrix. Then, each subshell (composed of the first two quantum numbers) is repeated as many times as required for each pair of electrons it may contain. The result is a compressed periodic table, with each entry representing two successive elements:
Like new
Stag arms from my 3H upper this is a quality gas block.
_____________________________
Railed Gas Block
Barrel size: .750"
Material: 7075 T6 Aluminum
Coating: Type 3 hard coat anodize
Picatinny Rail Height: .250" below the height of the rail on the receiver. Also knows as a "rail height...
My effort on a Sopmod Block II
Colt Upper Receiver
Daniel Defense 14.5 barrel
Daniel Defense RIS II Rail
Surefire 3 prong flash hider
Mega Lower
Tan Eotech 553 quick detach
$1450
*SOLD
Selling my mostly clone correct block II upper.
New colt upper, bcg, socom barrel
New DD handguard, surefire muzzle device (not pinned) and gasbuster CH
Used eotech, kac rear, and surefire light.
Assembled, shot 20rds, cleaned, and put in safe. Will not part out. Selling complete...
My Sopmod Block 2 effort in excellent/like new condition
Colt upper receiver
Daniel Defense 14.5 inch barrel
Surefire 3 prong flash hider pinned/welded
Daniel Defense RIS II rail
Mega Lower
Tan Eotech 553
$1350
Trades:
S&W 386 PD
Glock 40 plus cash
OD Gen 3 Glock 34 plus cash
Colt 6920...
Star Reproduction Remington Rolling Block Carbine in 30-30 cal. The barrel measures 20'' with open sights, single barrel band and saddle ring. The receiver is case colored and marked STAR-R. The plain straight stock ends in a case colored steel plate. Shows very light handling marks, very good...
How are you guys aligning your gas blocks?
Always looking for process improvements, my OCD causes me to spend a considerable amount of time ensuring everything is aligned properly for functionality and aesthetics.
SLR Sentry 8 Adjustable Gas Block
-.875"
- 15-position adjustability from 0 - 0.125" port opening
- Metering screw and screw bore design allows repeatability and reliability only SLR has been able to deliver
- Single tool click to adjust gas metering
- Melonite finish 4140 Precision machined...