When lithium reacts with bromine to form the compound libr each lithium atom
(1) gains one electron and becomes a negatively charged ion
(2) gains three electrons and becomes a negatively charged ion
(3) loses one electron and becomes a positively charged ion
(4) loses three electrons and becomes a positively charged ion

(3) loses one electron and becomes a positively charged ion

Explanation:

Lithium bromide is formed by combination of lithium cation and bromine anion.

Electronic configuration of lithium:

Lithium atom will loose one electron to gain noble gas configuration and form lithium cation with +1 charge.

Electronic configuration of bromine:

Bromine atom will gain one electron to gain noble gas configuration and form bromide ion with -1 charge.

In lithium bromide, one electron from lithium metal gets transferred to bromine atom.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

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