Its on Google..."The group number of a representative element in the periodic table is related to the number of valence electrons it has. ... Elements of the halogen family lose one electron to become halide ions."
Answer:
(NH4)2CO3 is the formula !
The enthalpy change : -196.2 kJ/mol
<h3>Further explanation </h3>
The change in enthalpy in the formation of 1 mole of the elements is called enthalpy of formation
The enthalpy of formation measured in standard conditions (25 ° C, 1 atm) is called the standard enthalpy of formation (ΔHf °)
(ΔH) can be positive (endothermic = requires heat) or negative (exothermic = releasing heat)
The value of ° H ° can be calculated from the change in enthalpy of standard formation:
∆H ° rxn = ∑n ∆Hf ° (product) - ∑n ∆Hf ° (reactants)
Reaction
2 H₂O₂(l)-→ 2 H₂O(l) + O₂(g)
∆H ° rxn = 2. ∆Hf ° H₂O - 2. ∆Hf °H₂O₂
The answer is the last option. Electronegativity is the measure of the attraction that an atom has for electrons involved in chemical bonds. It relates to covalent bonds where electrons are shared. The Pauling scale is the most used.