How do i know what to do and can you me because i really need it i am failing chemistry because it is too hard.

Exothermic:

An Exothermic reaction is a chemical reaction that expels energy in the form of heat/light. Everything a Endothermic does not do. Pretty simple for this one

reactants → products + energy.

For future reference - Exo means release, thermic means heat.

Energy is a Reactant

Endothermic:

An Endothermic reaction essentially is draining the heat energy from anything its its surroundings. Usually its just heat but can also be salt dissolving it water or ice melting. Another example would be frost on your windshield evaporating.

It is the exact opposite of an Exothermic reaction.

Energy is a Product

is there multiple choice answers?

- calcium has greater affinity to bond with electron receptors than hydrogen does and hence, it has the ability to replace hydrogen in most of its compounds.

- lithium has 2 valence electrons in the product because it can make only 1 bond with hydrogen. beryllium has 4 valence electrons in the product because it can only make 2 bonds. it has fewer electrons than neon and can react with electron donors. each hydrogen has 2 valence electrons, the same as helium.

- the covalent bond formed between carbon and hydrogen is polar because carbon is more electronegative than hydrogen and it attracts the bonded electron pair closer to itself, thus giving hydrogen a partial positive charge.

- a hydrogen bond is a relatively weak bond that hydrogen atoms make with the electronegative atoms nitrogen, oxygen or fluorine.

so the best choice is a.) 2 calcium (ca) atoms