When metals combine with nonmetals, the metallic atoms tend to 1. lose electrons and become positive ions 2. lose electrons and become negative ions 3. gain electrons and become positive ions 4. gain electrons and become negative ions?

1) lose electrons and become positive ions

Explanation:

To be able to solve this question, it is crucial to understand generally the chemistry of metals and non metals.

Generally metals are found in groups 1,2,3 in the periodic table. What these  tells us is that they have 1,2,3 electrons in their outermost shells. whenever metals want to go into reactions to complete their octet, it is much more feasible energy wise to lose those few electrons than accept about 5,6,7 more electrons.

When a compound loses its electron(s), it becomes a positive ion due to the net increase of protons compared to electrons.

For instance, calcium has 20 electrons and protons. However when it loses 2 electrons to complete its octet and become Ca2+, it still retains its 20 protons but the total number of electrons left is 20 -2 = 1 8. The difference between the protons and the electrons is usually what is represented by the charge on the ion.

However, the reverse is the case when it comes to nonmetals. Non metals would rather accept the few electrons as it is much feasible energy wise to complete its octet. Also, when  non metals gain electrons they would become negative ions due to the excess in number of electrons compared to protons.

As such, the only logical answer would be 1) lose electrons and become positive ions.

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

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.