Astable atom that has a large nucleus most likely contains 1. more neutrons than protons. 2.more protons than neutrons. 3.equal numbers of protons and neutrons. 4.changing numbers of protons and neutrons.

3.equal numbers of protons and neutrons.

Explanation:

A stable atom with a large nucleus would contain equal number of protons and neutrons. When the number of protons and neutrons in the nucleus are equal, an atom would attain stability.

Unstable atoms have either the number of protons or neutrons greater. In order for such atoms to attain stability, they give off the excess protons or neutrons. When atoms gives off excess protons or neutrons, they are said to be radioactive.

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.