7.8
(Its correct, I just took a quiz and it is the right answer. hope I helped.)
gas- less particles move fast and freely, not contained
liquid- particles move a bit slower, more particles
solid- particles barely move, many particles in a confined space
Answer:
You determine the weighted averages if the individual isotopic masses.
Procedure:
The atomic mass of Si is the <em>weighted average </em>of the atomic masses of its isotopes.
We multiply the atomic mass of each isotope by a number representing its relative importance (i.e., its percent abundance).
The three stable isotopes of Si are Si-28 (27.98 u, 92.22 %), Si-29 (28.98 u, 4.69 %), and Si-30 (29.97 u, 3.09 %).
Set up a table for easy calculation.
0.9222 × 27.89 u = <em>x</em> u
0.0469 × 28.98 u = <em>y</em> u
0.0309 × 29.97 u = <em>z</em> u
TOTAL = (<em>x</em>+<em>y</em>+<em>z</em>) u = atomic mass of Si.
Answer:
Helium is in the <u>Noble Gases</u> family. All elemnts in this family have <u>eight</u> valence electróns, except for Helium which has 2. Some chemical properties of elements in this family are <u>odorless</u><u> </u><u>and</u><u> </u><u>colorless</u><u>.</u>
Gray matter hope this helps!