When a lithium atom becomes ionized its new electron configuration is 4 points the same as which element?

A. Ar
B. Mg
C. He
D. Fe

C. He

Explanation:

When lithium is ionized, its new electronic configuration is the same as that of a helium atom.

 Lithium is made up of 3 electrons with a configuration of:

                     2, 1

it has 1 electron in its outermost shell.

As a metal lithium will prefer to lose an electron due to its electropositivity.

    On losing an electron, it will have 2 electrons remaining

Now, Helium has 2 electrons and this makes it similar to Lithium that has lost one electron.

This makes Lithium isoelectronic with Helium.  

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

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