Students in a science class prepared flash cards so that they could quiz one another about the arrangement of the periodic table. One of the flash cards contained information about two elements, Element L and Element M. Atoms of Element M have two more valence electrons than atoms of Element L.
Atoms of Element L are more reactive than atoms of Element M.
Both elements are metals.

Which of the answer choices fits the information given?

a. Sodium and Aluminum

b. Beryllium and Calcium

c. Silicon and Sulfur

d. Potassium and Calcium

i just learnt this recently but i need to look through my notes again

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.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.