As the atoms of the group 17 elements in the ground state are considered from top to bottom, each successive element has
(1) the same number of valence electrons and similar chemical properties
(2) the same number of valence electrons and identical chemical properties
(3) an increasing number of valence electrons and similar chemical properties
(4) an increasing number of valence electrons and identical chemical properties

Option (1) is the correct answer.

Explanation:

As each element of group 17 has 7 valence electrons. Therefore, they tend to show same type of reactivity.

And, when they react with another element then they tend to show a change in their chemical composition.

As a result, we can say that elements of group 17 show similar chemical properties due to the presence of same number of valence electrons.

Thus, we can conclude that as the atoms of the Group 17 elements in the ground state are considered from top to bottom, each successive element has  the same number of valence electrons and similar chemical properties.

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.