Beryllium (be): 1sc2sd, what's c and d?

C is equal to 2 and D is equal to 2.

Explanation:

Here C and D represents number of electrons in 1s and 2s orbitals.

Be has 4 electrons. Now, in order write electronic configuration of an atom, electron filling should be started from orbital with lowest energy.

Energy order of orbital with increasing energy: 1s< 2s< 2p< 3s< 3p< 4s< 3d....

So, filling of electron should start from 1s orbital then 2s, 2p, 3s, 3p and so on.

Each orbital can have maximum of 2 electrons.

So electronic configuration of Be is:

air quality

poor drinking water

and heavy polution

can lead to poor health

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g