What is the atomic number of an atom woth six valence electrons?
(A) 8
(B)10
(C) 12

8

Explanation:

The atomic mass of an atom refers to the number of protons in the nucleus of an atom. Hence, an element with 6 valence electron mean that it has 6 electrons in its outermost shell.

The atomic Number of elements with 6 valence electrons cannot necessarily be the same, however, elements with 6 valence electrons belong to group six on the periodic table.

From the options given above, :

Atomic number of 8 :

Configuration : 2, 6

Atomic number of 10 :

Configuration : 2, 8

Atomic number of 12 :

Configuration : 2, 8, 2

Hence, only the element with atomic number of 8 has 6 valence electrons in its outer most shell, hence, the answer.

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.