Which ones of this are an oxidation-reduction reaction? and why?
(A) Hcl (aq) → H+(aq) + cl-(aq) (B) CH4 + cl2 → CH3cl + Hcl
(C) 2 CrO4 2-+ 2H+ → Cr2O72-+ H2O (D) Zn + Hcl → Zncl 2 + H2

"the periodic table is arranged in order of atomic number."

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.

on passing the small ampere of electric current through the tube made of ar and hg of cfl generates uv rays which excites the fluorescent and thus emits the high radiation by consumption of just 5- 12 w in comparison to incandescent light which requires more power such as around 40 - 55 w to lighten.

moreover the life span of fluorescent or cfl is around 8000 h whereas the life span of incandescent is around 1200 h

hence, the building installed with incandescent lights bears more electricity bill.