Oxygen has 8 electrons, and its electronic configuration is 1s2 2s2 2p4.

Chloride ion has gained one electron, making its configuration 1s2 2s2 2p6 3s2 3p6.

The element with atomic number 12 is magnesium (Mg), and its electronic configuration is [Ne] 3s2.

The element with atomic number 15 is phosphorus (P), and its electronic configuration is [Ne] 3s2 3p3.

Chlorine (Cl) has the configuration 1s2 2s2 2p6 3s2 3p5.

The element with atomic number 20 is Calcium, which has the configuration [Ar] 4s2.

The element with atomic number 26 is iron (Fe), and its electronic configuration is [Ar] 4s2 3d6.

Copper (Cu) has the configuration [Ar] 4s2 3d9.

Iron (Fe) has 26 electrons, and its electronic configuration is [Ar] 4s2 3d6.

Nitrogen has 7 electrons, and its electronic configuration is 1s2 2s2 2p3.

The potassium ion (K+) loses one electron, resulting in the configuration 1s2 2s2 2p6.

Sodium ion (Na+) has lost one electron, resulting in the configuration 1s2 2s2 2p6.

Convert percentages to grams (assume 100 g total): 40 g C, 6.7 g H, 53.3 g O. Convert to moles: C=3.33, H=6.67, O=3.33. The simplest ratio is 1:2:1, giving CH2O.

Converting percentages to moles gives C: 40/12 = 3.33, H: 6.7/1 = 6.7, O: 53.3/16 = 3.33. The simplest ratio is 1:2:1, giving the empirical formula CH2O.

The empirical formula is the simplest whole number ratio, which is CH2O.

The empirical formula is the simplest whole number ratio of the elements in a compound. For glucose, it is CH2O.

The standard enthalpy of formation of CO2 is -393.5 kJ/mol.

The formation of water from hydrogen and oxygen is an exothermic reaction, resulting in a negative enthalpy change.

The enthalpy change for the formation of NaCl from its elements is -411 kJ.

At constant pressure, the enthalpy change is given by ΔH = ΔU + PΔV.

The standard enthalpy change for the formation of ammonia is -92.4 kJ.

The formation of water from hydrogen and oxygen is an exothermic reaction, thus the enthalpy change is negative.

The enthalpy change for the formation of 2 moles of water is -571.6 kJ.

The enthalpy change for the formation of CO2 from carbon and oxygen is -393.5 kJ/mol.

The enthalpy change for the formation of CO2 from its elements is -393.5 kJ/mol.

The decomposition of calcium carbonate is an endothermic reaction, requiring heat input.

The standard enthalpy change for the formation of water from its elements is -241.8 kJ/mol.

The formation of ammonia from nitrogen and hydrogen is an exothermic reaction, thus the enthalpy change is negative.

The enthalpy change when 1 mole of NaCl is dissolved in water is approximately -3.87 kJ.

The condensation of water vapor to liquid water releases heat, making the enthalpy change negative.