Noble gas notation for calcium

To find the noble gas notation, you first take the noble gas before the element you’re trying to find the notation for. In this case, the noble gas before Calcium is Argon. You put the symbol for Argon in square brackets, and then you write out the rest of the notation as you would normally.

This would look like [Ar]4s^2

The 4s^2 is because Calcium is the second element in the 4s columns (refer to the diagram)

Hope this helps :)

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

c. electrical charges of ionic bonds.