An unknown substance: - has a melting point of 1127 c,- is soluble in water,- does not conduct heat as a solid, andis hard. given these properties which of the following are possible identities for the unknown substance? 1.) al2.) cof23.) c (diamond)4.) sf6

The unknown substance is CoF2

Explanation:

Diamond is insoluble in water. It does not conduct electricity. Every atom in a diamond is bonded to its neighbours by four strong covalent bonds, leaving no free electrons and no ions .

Most diamonds are extremely efficient thermal conductors, but electrical insulators. Diamond conducts heat well as a result of the strong covalent bonds between carbon atoms in a diamond crystal.

The melting point of diamond is about 4027 °C.

Since the melting point of diamond is way higher, it's not soluble in water and diamond does conduct heat. The unknown substance is not diamond.

SF6 is slightly soluble in water.

SF6 is not hard but it's a gas.

The melting point of SF6 is about -64 °C

Since SF6 is a gas and not a solid and has a melting point way lower than the unknown substance; the unknown substance is not SF6

Aluminum is an excellent heat and electricity conducto

The melting point of Al is 660 °C

Since Al has a lower melting point and is a good heat conductor; the unknown substance is not aluminium.

CoF2 is sparingly soluble in water.

CoF2 has a melting point between 1100 °C and 1200 °C

CoF2 is a solid but a bad heat conductor

⇒ The unknown substance is CoF2

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

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