How does the number of valence electrons for elements change across a period? the number decreases. the number increases. the number stays constant. the number increases and then decreases for noble gases

Option (b) is the correct answer.

Explanation:

Valence electrons is the number of electrons present in the outermost shell of an atom.

So, when we move across a period from left to right then there will be increase in number of valence electrons.

For example, valence electrons in carbon is 4, nitrogen has 5 valence electrons, oxygen has 6 valence electrons.

Thus, we can conclude that number of valence electrons increases for elements change across a period.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.