Network solids are hard and have high melting points. which statement explains these properties?
a.
the atoms are held together with large networks of metallic bonds.
b.
the atoms are held together with large networks of electromagnetic forces.
c.
the atoms are held together with large networks of intermolecular forces.
d.
the atoms are held together with large networks of covalent bonds.

The correct answer is A the atoms are held together with large network of metallic bonds.

Explanation:

Metallic bond is a specific type of bond that is formed by interaction of many detached negatively charged electron with positively charged ions or cations,which provides a definite structure to the substance.

Due to the low ionization energy the electrons present in the outerorbital can be de localized throughout the metal.The de localized electrons able to freely move around the crystalline structure.

 There is a presence of strong interaction between negatively charged electrons and positively charged ions which is responsible for high melting and boiling point of metals.

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

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.